METHOD FOR PREPARING CONTINUOUS FIBER-REINFORCED CERAMIC MATRIX COMPOSITE BY FLASH SINTERING TECHNOLOGY

Abstract

The present disclosure discloses a method for preparing a continuous fiber-reinforced ceramic matrix composite by flash sintering technology, including: placing a continuous ceramic fiber preform in a mold, adding a nano-ceramic powder, and subjecting the resultant to mechanical oscillation and press forming in sequence to obtain a green body; heating the green body to a preset temperature and applying an electric field with a preset electric field intensity, until occurrence of flash sintering; and converting a power supply from a constant voltage state to a constant current state, holding at the temperature and cooling to obtain the continuous fiber-reinforced ceramic matrix composite.

Claims

1. A method for preparing a continuous fiber-reinforced ceramic matrix composite by flash sintering technology, comprising: 1) placing a continuous ceramic fiber preform in a mold, adding a nano-ceramic powder, and subjecting the resultant to mechanical oscillation and press forming in sequence to obtain a green body; 2) heating the green body to a preset temperature and applying an electric field with a preset electric field intensity, until occurrence of flash sintering; and 3) converting a power supply from a constant voltage state to a constant current state, holding at the temperature and cooling to obtain the continuous fiber-reinforced ceramic matrix composite.

2. The method of claim 1, wherein in step 1), the continuous ceramic fiber is at least one selected from the group consisting of a SiC fiber, an Al.sub.2O.sub.3 fiber and a ZrO.sub.2 fiber.

3. The method of claim 1, wherein in step 1), the continuous ceramic fiber preform comprises structurally one or more of a two-dimensional fiber cloth laminated preform, a three-dimensional needled preform and a 2.5-dimensional woven preform, and a volume fraction of the continuous ceramic fiber preform is in a range of 30-40%.

4. The method of claim 1, wherein in step 1), the nano-ceramic powder is at least one selected from the group consisting of a SiC powder, an Al.sub.2O.sub.3 powder and a ZrO.sub.2 powder, and the nano-ceramic powder has a particle size of 50-500 nm.

5. The method of claim 1, wherein in step 1), the mechanical oscillation is performed for 20-120 min; and the press forming is performed at a forming pressure of 100-300 MPa for 60-600 s.

6. The method of claim 1, wherein in step 2), the green body has an elongated shape or a cylindrical shape, and a length of the green body in a direction of the electric field is in a range of 1-30 cm.

7. The method of claim 1, wherein in step 2), the heating is performed at a rate of 2-20° C./min, and the preset temperature is in a range of 0.3T.sub.m-0.8T.sub.m, wherein T.sub.m is a melting temperature of the nano-ceramic powder.

8. The method of claim 1, wherein in step 2), the preset electric field intensity is in a range of 20-1000 V/cm.

9. The method of claim 1, wherein in step 3), in the constant current state, a current density is in a range of 10-500 mA/mm.sup.2.

10. The method of claim 1, wherein in step 3), the cooling comprises cooling to room temperature at a cooling rate of 5-30° C./min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 shows a scanning electron micrograph of the SiC fiber/SiC ceramic composite prepared in Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present disclosure will be illustrated in detail below with reference to the drawings and embodiments.

[0024] A method for preparing a continuous fiber-reinforced ceramic matrix composite by flash sintering technology is provided, which comprises the following steps:

[0025] 1) A two-dimensional fiber cloth laminated, a three-dimensional needled or a 2.5-dimensional woven SiC fiber, Al.sub.2O.sub.3 fiber or ZrO.sub.2 fiber is used as a continuous ceramic fiber preform, which is cut into the size of a mold and placed in the mold, wherein the mold has an elongated or cylindrical shape and a length of 1-30 cm, and a volume fraction of the fiber is in a range of 30-40%. Subsequently, SiC nano-ceramic powders, Al.sub.2O.sub.3 nano-ceramic powders or ZrO.sub.2 nano-ceramic powders with a particle size of 50-500 nm are gradually poured on the continuous ceramic fiber preform in the mold for several times with a small amount for each time. The nano-ceramic powders are made to fully fill the pores inside the continuous ceramic fiber preform by mechanical oscillation for 20-120 min, to obtain a loose composite.

[0026] 2) The loose composite is pressed at a forming pressure of 100-300 MPa for 60-600 s, to obtain a green body.

[0027] 3) The green body is placed in a flash sintering furnace, heated to a preset temperature of 0.3T.sub.m-0.8T.sub.m at a heating rate of 2-20° C./min (T.sub.m is the melting temperature of the nano-ceramic powder), and held at the temperature for 20-120 min.

[0028] 4) An electric field with a preset electric field intensity (20-1000 V/cm) is applied to both ends of the green body in the length direction, until the occurrence of flash sintering. Thereafter, the power supply is converted from a constant voltage state to a constant current state. The resultant is held at the temperature for 1-30 min at a preset current density (10-500 mA/mm.sup.2), and cooled to room temperature at a cooling rate of 5-30° C./min, to obtain the continuous fiber-reinforced ceramic matrix composite.

[0029] The following examples are carried out on the premise of the technical solutions of the present disclosure, illustrating the detailed embodiments and specific operation processes. However, the protection scope of the present disclosure will not be limited to the following examples.

Example 1

[0030] A method for preparing a continuous fiber-reinforced ceramic matrix composite by flash sintering technology was performed by the following steps:

[0031] 1) A three-dimensional needled SiC fiber preform was placed into a 2 cm×10 cm×2 cm elongated mold in a volume fraction of 40% of the mold size. Subsequently, SiC powders with a particle size of 300 nm were poured on the SiC fiber preform in the mold for 5 times. The SiC powders were made to fully fill the pores inside the SiC fiber preform by mechanical oscillation for 30 min, obtaining a loose composite.

[0032] 2) The loose composite was pressed at a forming pressure of 200 MPa for 120 s, obtaining a green body.

[0033] 3) The green body was placed in a flash sintering furnace, heated to a preset temperature of 1300° C. at a heating rate of 5° C./min, and held at the temperature for 30 min.

[0034] 4) An electric field with a preset electric field intensity of 100 V/cm was applied to both ends of the green body in the length direction, until the occurrence of flash sintering. Thereafter, the power supply was converted from a constant voltage state to a constant current state. The resultant was held at the temperature for 10 min at a preset current density of 200 mA/mm.sup.2, and cooled to room temperature at a cooling rate of 5° C./min, obtaining a SiC fiber/SiC ceramic composite.

[0035] The scanning electron micrograph of the SiC fiber/SiC ceramic composite prepared in this example is shown in FIG. 1. It can be seen from the FIGURE that the obtained composite has uniformly distributed matrix and compactness up to 97%, and the fiber has a desirable bonding with the interface. The tensile intensity of the obtained composite may reach up to 280 MPa, higher than the intensity (about 200 MPa) of the SiC fiber/SiC composite prepared by the conventional PIP method.

Example 2

[0036] A method for preparing a continuous fiber-reinforced ceramic matrix composite by flash sintering technology was performed by the following steps:

[0037] 1) A two-dimensional fiber cloth laminated SiC fiber preform was placed into a 4 cm×10 cm×2 cm elongated mold in a volume fraction of 30% of the mold size. Subsequently, SiC powders with a particle size of 200 nm were poured on the SiC fiber preform in the mold for 8 times. The SiC powders were made to fully fill the pores inside the SiC fiber preform by mechanical oscillation for 120 min, obtaining a loose composite.

[0038] 2) The loose composite was pressed at a forming pressure of 200 MPa for 240 s, obtaining a green body.

[0039] 3) The green body was placed in a flash sintering furnace, heated to a preset temperature of 1250° C. at a heating rate of 10° C./min, and held at the temperature for 30 min.

[0040] 4) An electric field with a preset electric field intensity of 200 V/cm was applied to both ends of the green body in the length direction, until the occurrence of flash sintering. Thereafter, the power supply was converted from a constant voltage state to a constant current state. The resultant was held at the temperature for 10 min at a preset current density of 300 mA/mm.sup.2, and cooled to room temperature at a cooling rate of 10° C./min, obtaining a SiC fiber/SiC ceramic composite. The tensile intensity of the obtained composite may reach up to 248 MPa, higher than the intensity (about 200 MPa) of the SiC fiber/SiC composite prepared by the conventional PIP method.

Example 3

[0041] A method for preparing a continuous fiber-reinforced ceramic matrix composite by using flash sintering technology was performed by the following steps:

[0042] 1) A 2.5-dimensional SiC fiber preform was placed into a 2 cm×10 cm×5 cm elongated mold in a volume fraction of 35% of the mold size. Subsequently, SiC powders with a particle size of 150 nm were poured on the SiC fiber preform in the mold for several times with a small amount for each time. The SiC powders were made to fully fill the pores inside the SiC fiber preform by mechanical oscillation for 60 min, obtaining a loose composite.

[0043] 2) The loose composite was pressed at a forming pressure of 300 MPa for 300 s, obtaining a green body.

[0044] 3) The green body was placed in a flash sintering furnace, heated to a preset temperature of 1300° C. at a heating rate of 2° C./min, and held at the temperature for 20 min.

[0045] 4) An electric field with a preset electric field intensity of 500 V/cm was applied to both ends of the green body in the length direction, until the occurrence of flash sintering. Thereafter, the power supply was converted from a constant voltage state to a constant current state. The resultant was held at the temperature for 15 min at a preset current density of 200 mA/mm.sup.2, and cooled to room temperature at a cooling rate of 10° C./min, obtaining a SiC fiber/SiC ceramic composite. The tensile intensity of the obtained composite may reach up to 265 MPa, higher than the intensity (about 200 MPa) of the SiC fiber/SiC composite prepared by the conventional PIP method.

Example 4

[0046] A method for preparing a continuous fiber-reinforced ceramic matrix composite by using flash sintering technology was performed by the following steps:

[0047] 1) A two-dimensional fiber cloth laminated Al.sub.2O.sub.3 fiber preform was placed into a φ 3 cm×10 cm cylindrical mold in a volume fraction of 30% of the mold size. Subsequently, Al.sub.2O.sub.3 powders with a particle size of 250 nm were poured on the Al.sub.2O.sub.3 fiber preform in the mold for 10 times. The Al.sub.2O.sub.3 powders were made to fully fill the pores inside the Al.sub.2O.sub.3 fiber preform by mechanical oscillation for 60 min, obtaining a loose composite.

[0048] 2) The loose composite was pressed at a forming pressure of 150 MPa for 300 s, obtaining a green body.

[0049] 3) The green body was placed in a flash sintering furnace, heated to a preset temperature of 1100° C. at a heating rate of 10° C./min, and held at the temperature for 60 min.

[0050] 4) An electric field with a preset electric field intensity of 1000 V/cm was applied to both ends of the green body in the length direction, until the occurrence of flash sintering. Thereafter, the power supply was converted from a constant voltage state to a constant current state. The resultant was held at the temperature for 10 min at a preset current density of 50 mA/mm.sup.2, and cooled to room temperature at a cooling rate of 10° C./min, obtaining an Al.sub.2O.sub.3 fiber/Al.sub.2O.sub.3 ceramic composite. The tensile intensity of the obtained composite may reach up to 239 MPa.

Example 5

[0051] A method for preparing a continuous fiber-reinforced ceramic matrix composite by using flash sintering technology was performed by the following steps:

[0052] 1) A two-dimensional fiber cloth laminated ZrO.sub.2 fiber preform was placed into a φ 5 cm×5 cm cylindrical mold in a volume fraction of 30% of the mold size. Subsequently, ZrO.sub.2 powders with a particle size of 500 nm were poured on the ZrO.sub.2 fiber preform in the mold for 6 times. The ZrO.sub.2 powders were made to fully fill the pores inside the ZrO.sub.2 fiber preform by mechanical oscillation for 120 min, obtaining a loose composite.

[0053] 2) The loose composite was pressed at a forming pressure of 250 MPa for 600 s, obtaining a green body.

[0054] 3) The green body was placed in a flash sintering furnace, heated to a preset temperature of 950° C. at a heating rate of 10° C./min, and held at the temperature for 30 min.

[0055] 4) An electric field with a preset electric field intensity of 1000 V/cm was applied to both ends of the green body in the length direction, until the occurrence of flash sintering. Thereafter, the power supply was converted from a constant voltage state to a constant current state. The resultant was held at the temperature for 15 min at a preset current density of 50 mA/mm.sup.2, and cooled to room temperature at a cooling rate of 15° C./min, obtaining a ZrO.sub.2 fiber/ZrO.sub.2 ceramic composite. The tensile intensity of the obtained composite may reach up to 233 MPa.

[0056] The embodiments described above are intended to facilitate those of ordinary skill in the art to understand and use the present disclosure. Obviously, those skilled in the art could easily make various modifications to these embodiments and apply the general principles as demonstrated here to other embodiments without creative work. Therefore, the present disclosure is not limited to the above embodiments. The improvements and modifications made by those skilled in the art based on the revelation of the present disclosure without departing from the scope of the present disclosure should fall within the protection scope of the present disclosure.