CN116102342B

CN116102342B - High damage tolerance alumina composite ceramic and preparation method thereof

Info

Publication number: CN116102342B
Application number: CN202310159733.9A
Authority: CN
Inventors: 苏云峰; 张永胜; 樊恒中; 宋俊杰; 魏万鑫; 胡丽天
Original assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Current assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Priority date: 2023-02-24
Filing date: 2023-02-24
Publication date: 2023-12-01
Anticipated expiration: 2043-02-24
Also published as: CN116102342A

Abstract

The invention discloses a preparation method of alumina composite ceramic with high damage tolerance, which comprises the steps of adding nano alumina powder and micron h-BN powder into distilled water, uniformly mixing, and adding polyethyleneimine for ball milling and mixing to obtain slurry; mixing chopped alumina fibers with the slurry, and uniformly distributing the mixture by ultrasonic stirring to obtain mixed slurry; drying the mixed slurry, and then placing the dried mixed slurry in a steel mould for compression molding to obtain a composite material blank; finally placing the ceramic in a graphite mold, adopting a spark plasma sintering technology to carry out pressurized sintering densification in a vacuum environment, and cooling to obtain the alumina composite ceramic with high damage tolerance. The invention utilizes the weak binding force of h-BN to induce crack tip deflection and bifurcation to redistribute load so as to achieve the aim of eliminating stress concentration of crack tipAnd promote Al ₂ O ₃ The fiber is pulled out to consume the breaking energy, so that the failure mode of brittle fracture of the material is improved, and the material has excellent service reliability, high critical crack size and damage tolerance.

Description

High damage tolerance alumina composite ceramic and preparation method thereof

Technical Field

The invention relates to an alumina composite ceramic and a preparation method thereof, in particular to an alumina composite ceramic with high damage tolerance and a preparation method thereof, belonging to the fields of composite materials and ceramic materials.

Technical Field

Alumina ceramic is used as the most widely used industrial oxide ceramic material at present, and has the advantages of high strength, low density, corrosion resistance, high temperature resistance and the like compared with the traditional metal and polymer materials, but the alumina is very sensitive to defects due to the influence of strong ionic covalent bonds of the alumina, so that the alumina ceramic has lower damage tolerance, and unexpected catastrophic fracture usually occurs, so that the wide application of the alumina ceramic as a structural member is limited to a certain extent.

Based on the teaching of the biological material structure, the microstructure of the material is constructed into a layered structure or a fiber reinforced composite material, the structural characteristics are utilized to realize the influence on the crack propagation of the material, and the local load is continuously redistributed by inducing crack deflection, bridging and bifurcation, so that the crack tip stress is eliminated, the damage capacity limit of the material is improved to a certain extent, and the material shows a non-brittle fracture behavior. The internal interface phase (layer) of the material plays a vital role and function for the mode of realizing material toughening and improving service reliability by utilizing an external toughening mechanism. The bonding strength of the interface phase determines the crack induction capability and the time for inducing the crack to occur, and the interface phase with proper material matrix performance can not only greatly improve the toughness of the material, but also maintain the strength to the greatest extent. Chinese patent (CN 1884189A) discloses a preparation method of fiber toughened alumina ceramic matrix composite, which comprises ball milling alumina powder, cosolvent and absolute ethanol for 72-90 hours, drying, sieving, pretreatingThe mullite short fiber is ball-milled and granulated with the powder and the polyvinyl alcohol, pressed into a sheet, dried and finally sintered and molded under no pressure at 1450-1500 ℃. However, the method is used as a combination mode of a strong-strong interface, does not highlight the induction of cracks, and leads to limited improvement degree of R curve behavior and damage tolerance of the material. At present, the comprehensive mechanical properties of ceramics are generally improved by introducing an interface layer with proper strength. Chinese patent (CN 106966703A) discloses a preparation method of alumina fiber reinforced alumina ceramic containing interface phase, which comprises preparing pyrolytic carbon PyC interface phase on the surface of alumina fiber by methane through vapor deposition method, repeatedly impregnating alumina gel to densify, and finally obtaining fracture toughness of 5.2 MPa.m ^1/2 . But the bending strength is only 92.3 MPa. Therefore, the interface layer introduced by the method is very important, the introduction is unreasonable, the composite material with the non-brittle fracture characteristic cannot be obtained, and other mechanical properties can be seriously influenced.

Disclosure of Invention

In order to overcome the problems of high brittleness, high defect sensitivity and easy occurrence of catastrophic fracture of the alumina ceramic, the invention aims to provide a preparation method of the alumina composite ceramic with high damage tolerance, and the alumina composite ceramic with excellent mechanical properties, high critical crack size and damage tolerance is obtained through a simple and green preparation process so as to meet the safe and reliable service requirements of mechanical parts under severe working conditions.

The invention provides a preparation method of alumina composite ceramic with high damage tolerance, which comprises the following steps:

(1) Nano Al ₂ O ₃ Adding the powder and the micron h-BN powder into distilled water, uniformly mixing, and adding Polyethyleneimine (PEI) for ball milling and mixing to obtain uniform interfacial phase slurry.

The Al is ₂ O ₃ The powder size is 80-120 nm, the h-BN size is about 2-10 mu m, al ₂ O ₃ And the volume ratio of h-BN is 3:7-1:1. The molecular weight of the polyethyleneimine is 10000, and the addition amount of the polyethyleneimine is powder (nano Al ₂ O ₃ Powder and micron h-BN powder) of 2% -5% of the total mass.

The ball milling time is 12-48 h, and the speed is 100-200 r/min.

The interfacial phase slurry can also be prepared by adding h-BN powder into a hydroxy alumina sol solution for ball milling and mixing, and the hydroxy alumina sol can be converted into Al after sintering ₂ O ₃ The content ratio thereof can be determined by molar amount conversion. The aluminum hydroxide sol has certain viscosity and viscosity, and meanwhile, the introduction of PEI organic matters can be avoided, so that better compactness is achieved.

(2) And mixing the cleaned chopped alumina fibers with the interfacial phase slurry, and uniformly distributing the mixture by ultrasonic stirring to obtain mixed slurry.

The alumina fiber is cleaned by mixing Al ₂ O ₃ The fiber is subjected to ultrasonic vibration in absolute ethyl alcohol to clean impurities on the surface of the fiber. Cutting into Al with the fiber diameter of 10-12 mu m and the length of 0.5-4 mm after cleaning ₂ O ₃ And (3) fibers.

The dosage of the alumina fiber is measured according to the volume ratio of the alumina fiber to the solid phase content in the interfacial phase slurry of 3:1-9:1.

(3) And (3) drying the mixed slurry, and then placing the dried mixed slurry in a steel mould for compression molding to obtain a composite material blank.

In the drying process of the sizing agent, the water is heated and evaporated while stirring until the water is evaporated to dryness. The process of heating and evaporating water while stirring can further promote the uniform mixing of the fiber and the powder. The drying temperature is controlled to be 50-90 ℃.

In the compression molding, the dry pressure is 100-250 MPa, and the pressure maintaining time is 5-11 min. Because PEI has certain viscosity, powder is facilitated to be adhered to the surface of the fiber, and certain viscosity is provided to avoid excessively rapid sedimentation of the fiber.

(4) And placing the obtained composite material blank in a graphite mold, adopting a Spark Plasma Sintering (SPS) technology to perform pressurized sintering densification in a vacuum environment, and cooling to obtain the alumina composite ceramic with high damage tolerance.

The pressure sintering process comprises the following steps: the temperature rising rate is 100-130 ℃/min, the sintering temperature is 1300-1600 ℃, the pressure is 5-20 MPa, the temperature is kept for 6-12 min, and the vacuum degree is less than 100 Pa. And (3) PEI is heated and decomposed in the sintering process, and finally the alumina composite ceramic with high damage tolerance is obtained.

The mechanism for preparing the alumina composite ceramic with high damage tolerance is as follows: the weak binding force of h-BN is utilized to induce crack tip deflection and bifurcation to redistribute load so as to achieve the aim of eliminating stress concentration of crack tip and promote Al ₂ O ₃ The fiber is pulled out to consume the breaking energy, so that the failure mode of brittle fracture of the material is improved, and the material has excellent service reliability, high critical crack size and damage tolerance. In addition, by introducing Al in the h-BN weak interface ₂ O ₃ To regulate and control the binding force, thereby realizing the regulation and control of the strength and toughness of the composite material.

Drawings

FIG. 1 is an XRD pattern of the high damage tolerant alumina composite ceramic prepared in example 1.

FIG. 2 is a graph of crack propagation paths of the high damage tolerant alumina composite ceramic prepared in example 1.

FIG. 3 is a cross-sectional view of the high damage tolerant alumina composite ceramic prepared in example 1.

FIG. 4 is a graph of crack propagation resistance of the high damage tolerant alumina composite ceramic prepared in examples 1-4.

Detailed Description

The method and performance of the present invention for preparing a high damage tolerant alumina composite ceramic can be further illustrated by the following examples.

Example 1

0.37g of Al ₂ O ₃ Adding the powder and 0.49g h-BN powder into 50 ml distilled water, uniformly mixing, adding 50 g aluminum oxide grinding balls and 0.02 g polyethyleneimine, and ball-milling 48 h to form uniform interfacial phase slurry; mixing the chopped alumina fibers cleaned by 11.10 and g with the interfacial phase slurry, and uniformly distributing the mixture by ultrasonic stirring; drying the mixed slurry, placing the dried mixed slurry into a steel mold, and dry-pressing the dried mixed slurry into a blank under 100 MPa for 5 min; then placing the blank into a graphite die, sintering by using discharge plasma at 1300 ℃ and 20 MPa, heating at a rate of 100 ℃/min, and preserving heat for 6 min; and cooling to obtain the high damage tolerance alumina composite ceramic.

As shown in figure 1, the spectrum of the sample material is obtained by XRD analysis, and the ceramic is mainly composed of h-BN and Al ₂ O ₃ Composition is prepared.

Fig. 2 is a ceramic crack propagation path diagram of a sample material, and it can be seen that the crack propagation process has obvious deflection, bifurcation and other behaviors, which shows that the ceramic crack propagation path diagram has good crack tolerance.

Fig. 3 is a cross-sectional view of a sample material, showing the uniform distribution of fibers and the behavior of a large number of fibers pulled out during the breaking process.

FIG. 3 is a graph of crack propagation resistance for a sample material, showing that material fracture exhibits typical non-brittle fracture with excellent service reliability.

The critical crack size is 37.28 + -13.71 μm, and the damage tolerance parameter is 0.570+ -0.045 m ^1/2 。

Example 2

0.74g of Al ₂ O ₃ Adding the powder and 0.63g h-BN powder into 50 ml distilled water, uniformly mixing, adding 50 g alumina grinding balls and 0.04 g polyethyleneimine, ball milling 36 h, and forming uniform interfacial phase slurry; mixing the chopped alumina fibers cleaned by 10.49 and g with the interfacial phase slurry, and uniformly distributing the mixture by ultrasonic stirring; drying the mixed slurry, placing the dried mixed slurry into a steel mold, and dry-pressing the dried mixed slurry into a blank under 150 MPa for 7 min; then placing the blank into a graphite die, sintering by using discharge plasma at 1400 ℃ and 15 MPa, heating at a rate of 110 ℃/min, and preserving heat for 8 min; and cooling to obtain the high damage tolerance alumina composite ceramic. The critical crack size is 105.47 +/-19.11 mu m, and the damage tolerance parameter is 0.714+/-0.061 m ^1/2 The crack propagation resistance diagram is shown in fig. 4.

Example 3

1.24g of Al ₂ O ₃ Adding the powder and 0.70g h-BN powder into 50 ml distilled water, uniformly mixing, adding 50 g aluminum oxide grinding balls and 0.08 g polyethylenimine, and ball-milling 24, 24 h to form uniform interfacial phase slurry; mixing the chopped alumina fibers cleaned by 9.87. 9.87 g with the interfacial phase slurry, and uniformly distributing the chopped alumina fibers by ultrasonic stirring; drying the mixed slurry, placing the dried mixed slurry into a steel mould, and placing the dried mixed slurry into a steel mould200 Dry-pressing under the pressure of MPa to form a blank, wherein the pressure maintaining time is 9 min; then the blank is put into a graphite mould and sintered by using discharge plasma under the conditions of 1500 ℃ and 10 MPa, the heating rate is 120 ℃/min, and the heat preservation is carried out for 10 min; and cooling to obtain the high damage tolerance alumina composite ceramic. The critical crack size is 72.50 plus or minus 18.75 mu m, and the damage tolerance parameter is 0.627 plus or minus 0.093 m ^1/2 The crack propagation resistance diagram is shown in fig. 4.

Example 4

1.85g of Al ₂ O ₃ Adding the powder and 0.70g h-BN powder into 50 ml distilled water, uniformly mixing, adding 50 g alumina grinding balls and 0.13 g polyethylenimine, ball-milling 24, 24 h to form uniform interface phase slurry, mixing 9.25 g cleaned chopped alumina fibers with the interface phase slurry, and uniformly distributing by ultrasonic stirring; drying the mixed slurry, placing the dried mixed slurry into a steel mold, and dry-pressing the dried mixed slurry into a blank under 250 MPa, wherein the pressure maintaining time is 11 min; then placing the blank into a graphite mold, sintering by using discharge plasma at 1600 ℃ and 5 MPa, heating at a rate of 130 ℃/min, and preserving heat for 12 min; and cooling to obtain the high damage tolerance alumina composite ceramic. The critical crack size is 83.95 +/-19.42 mu m, and the damage tolerance parameter is 0.674+/-0.066 m ^1/2 The crack propagation resistance diagram is shown in fig. 4.

In the above embodiment, al ₂ O ₃ The powder size is 80-120 nm, the h-BN size is about 2-10 mu m, and the chopped alumina fiber is prepared by mixing Al ₂ O ₃ The fiber is chopped into fibers with the diameter of about 5 mu m and the length of about 2mm after the surface impurities of the fiber are cleaned by ultrasonic vibration in absolute ethyl alcohol.

Claims

1. A method for preparing an alumina composite ceramic with high damage tolerance, comprising the steps of:

(1) Nano Al ₂ O ₃ Adding the powder and the micron h-BN powder into distilled water, uniformly mixing, and then adding polyethyleneimine for ball milling and mixing to obtain uniform interfacial phase slurry; al (Al) ₂ O ₃ The powder size is 80-120 nm, the h-BN size is 2-10 mu m, al ₂ O ₃ And the volume ratio of h-BN is 3:7-1:1;

(2) Mixing the cleaned chopped alumina fibers with the interface phase slurry, and uniformly distributing the mixture by ultrasonic stirring to obtain mixed slurry; the diameter of the chopped alumina fiber is 10-12 mu m, and the length is 0.5-4 mm; the dosage of the chopped alumina fiber is measured according to the volume ratio of the chopped alumina fiber to the solid phase content in the interfacial phase slurry of 3:1-9:1;

(3) Drying the mixed slurry, and then placing the dried mixed slurry in a steel mould for compression molding to obtain a composite material blank; in the compression molding, the dry pressure is 100-250 MPa, and the pressure maintaining time is 5-11 min;

(4) Placing the obtained composite material blank in a graphite mold, adopting a spark plasma sintering technology to carry out pressurized sintering densification in a vacuum environment, and cooling to obtain the high damage tolerance alumina composite ceramic; the pressure sintering process comprises the following steps: the temperature rising rate is 100-130 ℃/min, the sintering temperature is 1300-1600 ℃, the pressure is 5-20 MPa, the temperature is kept for 6-12 min, and the vacuum degree is less than 100 Pa.

2. The method for preparing the alumina composite ceramic with high damage tolerance according to claim 1, wherein: in the step (1), the molecular weight of the polyethyleneimine is 10000, and the addition amount of the polyethyleneimine is 2% -5% of the total mass of the powder.

3. The method for preparing the alumina composite ceramic with high damage tolerance according to claim 1, wherein: in the step (1), the ball milling time is 12-48 hours, and the speed is 100-200 r/min.

4. The method for preparing the alumina composite ceramic with high damage tolerance according to claim 1, wherein: in the step (1), the interfacial phase slurry is prepared by adding h-BN powder into a hydroxyl alumina sol solution for ball milling and mixing.

5. The method for preparing the alumina composite ceramic with high damage tolerance according to claim 1, wherein: in the step (3), the slurry is dried, and the water is heated and evaporated while stirring until the water is evaporated; the drying temperature is controlled to be 50-90 ℃.