A lithium-aluminum-silicon glass-ceramic composite material reinforced by pre-oxidized cubic boron nitride and carbon fibers and a preparation method thereof

Abstract

This invention provides a lithium aluminum silicon glass-ceramic composite material synergistically reinforced with pre-oxidized cubic boron nitride and carbon fiber, and its preparation method. LAS powder and pre-oxidized cubic boron nitride powder are mixed uniformly, and then an aqueous dispersion containing a dispersant is added. The mixture is ball-milled to obtain a slurry, which is then uniformly coated onto carbon fiber cloth. After thorough impregnation, the slurry is dried to obtain a prepreg. Multiple layers of prepreg are stacked in the same direction to obtain a laminate, which is sintered under vacuum or an inert atmosphere. After cooling, a Cf / LAS composite material is obtained. By designing a special particle structure of "boron oxide-coated cBN core," a tight bond between the reinforcing phase and the matrix is ​​achieved, and the overall interface system of the composite material is precisely controlled, ultimately obtaining excellent comprehensive properties of high strength, high toughness, high hardness, and low wear rate.

Description

Technical Field

[0001] This invention belongs to the field of ceramic matrix composite technology, specifically relating to a lithium aluminum silicon glass-ceramic composite material synergistically reinforced with pre-oxidized cubic boron nitride and carbon fiber, and its preparation method. Background Technology

[0002] Carbon fiber reinforced lithium aluminum silicon glass-ceramic composites (Cf / LAS) are ideal candidate materials for manufacturing ultra-high precision optical devices, space telescope structural components, and precision measurement reference platforms due to their near-zero coefficient of thermal expansion and excellent thermomechanical stability. However, their relatively soft glass-ceramic matrix results in low surface hardness and poor wear resistance, making them prone to scratches and wear during assembly, fretting, or service friction, directly affecting the long-term accuracy and reliability of the system.

[0003] To overcome this deficiency, introducing ultrahard second-phase particles is a direct and effective approach. Cubic boron nitride (cBN) has extremely high hardness, which can significantly improve the hardness and abrasive wear resistance of composite materials. However, traditional cBN particles have high surface inertness and generally poor physicochemical compatibility with LAS glass-ceramic matrices. They are prone to agglomeration during sintering, and the interfacial bonding with the matrix is ​​often too weak or (due to localized reactions at high temperatures) too rigid, making it difficult to control. Insufficient bonding leads to particle detachment in the early stages of wear, resulting in a loss of reinforcement; excessive bonding may induce brittle fracture, impairing the material's intrinsic toughness. Therefore, simply mechanically incorporating cBN particles often faces the dilemma of low reinforcement efficiency, difficulty in interface optimization, and limited performance improvement. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a lithium aluminum silicon glass-ceramic composite material synergistically reinforced with pre-oxidized cubic boron nitride and carbon fiber, and its preparation method, achieving the following objectives: improving the compatibility between cBN and LAS glass-ceramic matrix, improving the interfacial bonding performance between cBN and LAS glass-ceramic matrix, and enhancing the performance improvement effect of cBN on existing Cf / LAS composite materials.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a lithium aluminum silicon glass-ceramic composite material synergistically reinforced with pre-oxidized cubic boron nitride and carbon fiber involves uniformly mixing LAS powder and pre-oxidized cubic boron nitride powder, adding an aqueous dispersion containing a dispersant, ball milling to obtain a slurry, uniformly coating it onto carbon fiber cloth, fully impregnating it, drying it to obtain a prepreg, stacking multiple layers of prepreg in the same direction to obtain a laminate, sintering it under vacuum or inert atmosphere protection, and cooling it to obtain a Cf / LAS composite material.

[0006] The pre-oxidized cubic boron nitride powder has a mass percentage of 1-5% relative to the LAS powder, preferably 2-2.5%.

[0007] The method for preparing the pre-oxidized cubic boron nitride powder is as follows: raw cBN powder is heated from room temperature to 680-720℃ at a rate of 4.5-5.5℃ / min in an oxygen-containing atmosphere, held at a constant temperature for 115-125 minutes, and then naturally cooled to obtain the pre-oxidized cubic boron nitride powder.

[0008] The pre-oxidized cubic boron nitride has a core-shell structure, with the core being cubic boron nitride (cBN) and the outer shell being an amorphous coating layer of boron oxide (B2O3).

[0009] The average particle size of the original cBN powder is 0.8-1.2 μm; the oxygen-containing atmosphere is an air atmosphere.

[0010] The average particle size of the LAS powder is 2.4-2.6 μm, the mass-to-volume ratio of the LAS powder to the aqueous dispersion containing the dispersant is 1 g: 1.8-2.2 mL, and the mass concentration of the dispersant in the aqueous dispersion is 0.45-0.55%.

[0011] The dispersant is an aqueous dispersant; The aqueous dispersant is ammonium polyacrylate; The coating amount of the slurry on the carbon fiber cloth is 2100-2300 g / m. 2 The thickness of the prepreg is 0.9-1.1 mm.

[0012] The multilayer prepreg has 19-21 layers, and the volume fraction of carbon fiber cloth in the composite material is 38-42%.

[0013] The specific sintering method is to raise the temperature to 1340-1360℃ at a rate of 4.8-5.2℃ / min, apply an axial pressure of 24-26MPa, and hold the temperature and pressure for 28-32 minutes.

[0014] The composite material obtained by the preparation method is described above.

[0015] The sintered and dense composite material block is cut, ground, and polished to produce parts or samples with the required shape and surface precision.

[0016] Compared with the prior art, the present invention achieves the following beneficial effects: (1) This invention provides a lithium aluminum silicon glass ceramic composite material with pre-oxidized cubic boron nitride and carbon fiber synergistic reinforcement and its preparation method. By designing a special particle structure of "boron oxide coated cBN core", the reinforcing phase and the matrix are tightly bonded. The overall interface system of the composite material is precisely controlled, and finally, excellent comprehensive performance with high strength, high toughness, high hardness and low wear rate is obtained.

[0017] (2) By pre-oxidizing cBN, the boron oxide shell formed by pre-oxidation has good chemical compatibility and wettability with the LAS glass-ceramic matrix at high temperature, which promotes the formation of a strong and tough interface between cBN particles and the matrix, avoids particle detachment, and gives full play to the load-bearing role of its hard reinforcing phase.

[0018] (3) By optimizing the amount of pre-oxidized cBN added, this invention can simultaneously achieve significant strengthening and toughening effects and improved wear resistance. An appropriate amount of pre-oxidized cBN (e.g., 2-2.5 wt.%) can induce the formation of a fine structure at the carbon fiber-matrix interface that facilitates energy dissipation, thereby maintaining or even improving the fracture toughness of the material while increasing hardness. The Cf / LAS composite material prepared by adding 2-2.5 wt.% pre-oxidized cBN exhibits a flexural strength of 890.4-905.6 MPa, a fracture toughness of 21.5-21.8 MPa·m¹ / ², a Vickers hardness (9.8 N load) of 698.7-735.4 HV, and a volumetric wear rate of 2.31-2.52 × 10⁻⁶. -6 mm³ / (N·m).

[0019] (4) The subsequent slurry preparation and hot-pressing sintering process of this invention is highly compatible with the existing Cf / LAS composite material preparation process, and is easy to achieve large-scale production. By adjusting the content of pre-oxidized cBN, the performance spectrum of the composite material can be "tailored". Low content focuses on optimizing strength and toughness, which is suitable for structural load-bearing components; high content focuses on maximizing hardness and wear resistance, which is suitable for wear-resistant surfaces or components. Attached Figure Description

[0020] Figure 1 Transmission electron microscopy image of the pre-oxidized cBN powder prepared in Example 1; (a) is a transmission electron microscope view of the pre-oxidized cBN powder; (b) is a magnified view of a part of it.

[0021] Figure 2 Fracture morphology images of the Cf / LAS composite materials prepared in Examples 2-7; (a) is a fracture morphology diagram of the Cf / LAS composite material prepared in Example 2; (b) is a fracture morphology diagram of the Cf / LAS composite material prepared in Example 3; (c) is a fracture morphology diagram of the Cf / LAS composite material prepared in Example 4; (d) is a fracture morphology diagram of the Cf / LAS composite material prepared in Example 5; (e) is a fracture morphology diagram of the Cf / LAS composite material prepared in Example 6; and (f) is a fracture morphology diagram of the Cf / LAS composite material prepared in Example 7. Figure 3 Transmission electron microscopy (TEM) images of the Cf / LAS composite materials prepared in Examples 2, 5, and 7; (a) is a transmission electron microscope (TEM) image of the Cf / LAS composite material prepared in Example 2; (b) is a TEM image of the Cf / LAS composite material prepared in Example 5; and (c) is a TEM image of the Cf / LAS composite material prepared in Example 7. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the invention.

[0023] Example 1: Preparation of pre-oxidized cBN powder Approximately 50g of raw cBN powder was placed in a corundum crucible and spread to a thickness of about 5mm. Its average particle size (D50) was 1.0μm, and its purity was >99.9% (purchased from Element Six). The crucible was placed in the homogenization zone of a muffle furnace (KSL-1700X type) and heat-treated in air. The temperature was increased from room temperature to 700℃ at a rate of 5℃ / min, held at that temperature for 120 minutes, and then the power was turned off. The furnace was allowed to cool naturally to room temperature, yielding a light gray pre-oxidized cBN powder, abbreviated as O-cBN.

[0024] Transmission electron microscopy (TEM) images of the pre-oxidized cBN powder showed that a uniform layer of boron oxide (B2O3) amorphous coating was formed on the surface of the cBN crystal nuclei (see [link to TEM image]). Figure 1 ).

[0025] Example 2: Preparation and performance testing of the benchmark material (0 wt.% cBN) This embodiment serves as a benchmark for performance comparison, preparing a Cf / LAS composite material without cBN reinforcing phase.

[0026] (1) Preparation of prepreg 100 g of LAS powder (average particle size 2.5 μm) was dispersed in 200 mL of 0.5 wt.% ammonium polyacrylate (PAA) aqueous dispersion and ball-milled for 4 hours to obtain a uniform LAS slurry. The areal density was 200 g / m³. 2 T300 unidirectional carbon fiber cloth (Toray) is used as the reinforcing fiber. LAS slurry is coated onto the carbon fiber cloth (2200 g / m²). 2 The slurry is rolled to ensure even distribution, then left to stand for 10 minutes to ensure full impregnation, and then dried at 80°C for 12 hours to obtain the prepreg.

[0027] The roller pressing has a pressing pressure of 10N and a pressing speed of 1cm / s; The thickness of the prepreg is 1 mm.

[0028] (2) Preparation of Cf / LAS composite material Approximately 20 layers of prepreg are stacked in the same direction in a graphite mold coated with BN release agent. The mixture is then heated in a hot press (HP-2020 type) under vacuum (10... -2 Sintering was carried out at 1350°C with a heating rate of 5°C / min, and an axial pressure of 25 MPa was applied and held for 30 minutes. The mixture was then cooled in the furnace to obtain the Cf / LAS composite material.

[0029] The density of the Cf / LAS composite material is 2.10 g / cm³. 3 The open area ratio is 1.6%, the three-point bending strength is 482.3±13.5MPa, the fracture toughness is 15.2±1.5MPa·m¹ / ², the Vickers hardness (9.8N load) is 443.4±45.2HV, and the volumetric wear rate is 3.00×10⁻⁶. -6 mm³ / (N·m).

[0030] The volume fraction of carbon fiber cloth in the Cf / LAS composite material is 40 vol.%.

[0031] Examples 3-7: Cf / LAS composites with different contents of pre-oxidized cBN (O-cBN) This series of examples systematically studies the effect of O-cBN content (1, 2, 2.5, 3, 5 wt.%) on the properties of composite materials. The preparation process is exactly the same as in Example 2, except that LAS powder and O-cBN powder are first dry-mixed for 5 minutes and then dispersed in 200 mL of deionized water containing 0.5 wt.% ammonium polyacrylate (PAA) dispersant.

[0032] All O-cBN powders used were prepared in Example 1; The amounts of O-cBN powder added were 1, 2, 2.5, 3, and 5 wt.% (based on the mass of LAS powder).

[0033] Table 1: Comprehensive performance data of composite materials prepared in Examples 2-7

[0034] As can be seen from Table 1: The composite material prepared in Example 5 (O-cBN content 2.5 wt.%) exhibited the best overall performance balance. Its strength, toughness, and hardness were increased by approximately 87.8%, 43.4%, and 66% respectively compared to the baseline (Example 2), while the wear rate was reduced by 23%.

[0035] The mechanical properties (strength and toughness) of the composite materials in Examples 2-7 showed a trend of first significantly increasing and then decreasing with the O-cBN content, reaching a peak at 2-2.5 wt.%; while the hardness increased monotonically, and the wear rate continued to decrease before stabilizing.

[0036] Fracture morphology images of the Cf / LAS composite materials prepared in Examples 2-7 are shown below. Figure 2 .

[0037] The fracture roughness of the Cf / LAS composite material described in Examples 4 (2 wt.%) and 5 (2.5 wt.%) was... Figure 2 (c) and (d) show a large number of long fibers pulled out (>100μm) and deep pores, which are typical ductile fracture characteristics, indicating that the interfacial bonding strength has been optimized to the best.

[0038] The fracture surface of the Cf / LAS composite material prepared in Example 7 (5 wt.%) was flat. Figure 2 (f) The fibers mostly fracture flush with each other, with very few pulled out, indicating that the interface is too strong, leading to brittle fracture.

[0039] The Cf / LAS composite material prepared in Example 2 (0 wt.%) showed significant fiber pull-out, debonding, and crack deflection, but the matrix was relatively loose with micropores, resulting in relatively low composite strength. Figure 2 (a)

[0040] The Cf / LAS composite material prepared in Example 3 (1 wt.%) had a relatively dense matrix, with obvious fiber pull-out and debonding. The strength and toughness of the composite material were both improved. Figure 2 (b)).

[0041] The Cf / LAS composite material prepared in Example 6 showed that the fiber pull-out length began to shorten, the bond strength between the fiber and the matrix increased, and the load transfer capacity increased, but the fracture toughness decreased. Figure 2 (e)).

[0042] Transmission electron microscopy (TEM) images of the Cf / LAS composite materials prepared in Examples 2, 5, and 7 are shown below. Figure 3 As shown.

[0043] The Cf / LAS composite material prepared in Example 5 formed a unique interface layer of approximately 100 nm between the carbon fiber and the LAS matrix. Figure 3 (b) presents a “brick-mortar” nanostructure (ordered graphite microcrystals embedded in an amorphous matrix).

[0044] The Cf / LAS composite material prepared in Example 2, without the addition of c-BN, achieved an interface layer thickness of 385 nm. Figure 3 (a)).

[0045] The Cf / LAS composite material prepared in Example 7 had 5 wt.% O-cBN added. The amount added was too high, and the interfacial layer of the composite material almost disappeared. Figure 3 (c)).

[0046] During sintering, the B2O3 coating layer on the O-cBN surface interacts with the LAS melt, catalyzing the in-situ growth of ordered graphite microcrystals in the interface region, thereby constructing a weakly bonded interface layer that facilitates energy dissipation.

[0047] Example 8 uses Cf / LAS composite material with untreated cBN (2.5 wt.%). Except for completely replacing O-cBN with untreated raw cBN powder (same as the raw material in Example 1, 2.5 wt.%), the preparation method was the same as in Example 5.

[0048] The material obtained in Example 8 has a flexural strength of 785.2 ± 20.1 MPa, a fracture toughness of 18.6 ± 1.8 MPa·m¹ / ², a Vickers hardness of 705.8 ± 68.4 HV, and a volumetric wear rate of 2.60 × 10⁻⁶. -6 mm³ / (N·m).

[0049] As can be seen, the Cf / LAS composite materials prepared using untreated cBN are significantly inferior to those prepared in Example 5 using O-cBN. This indicates that the boron oxide shell formed by pre-oxidation plays an irreplaceable and crucial role in improving particle dispersion, optimizing interfacial bonding, and thus comprehensively enhancing overall performance.

Claims

1. A method for preparing a lithium aluminum silicon glass-ceramic composite material synergistically reinforced with pre-oxidized cubic boron nitride and carbon fiber, characterized in that: After uniformly mixing LAS powder and pre-oxidized cubic boron nitride powder, an aqueous dispersion containing a dispersant is added, and the mixture is ball-milled to obtain a slurry. This slurry is then uniformly coated onto carbon fiber cloth, fully impregnated, and dried to obtain a prepreg. Multiple layers of prepreg are stacked in the same direction to obtain a laminate, which is then sintered under vacuum or inert atmosphere protection. After cooling, a Cf / LAS composite material is obtained.

2. The preparation method according to claim 1, characterized in that: The pre-oxidized cubic boron nitride powder has a mass percentage of 1-5% relative to the LAS powder.

3. The preparation method according to claim 1, characterized in that: The pre-oxidized cubic boron nitride powder has a mass percentage of 2-2.5% relative to the LAS powder.

4. The preparation method according to claim 1, characterized in that: The method for preparing the pre-oxidized cubic boron nitride powder is as follows: raw cBN powder is heated from room temperature to 680-720℃ at a rate of 4.5-5.5℃ / min in an oxygen-containing atmosphere, held at a constant temperature for 115-125 minutes, and then naturally cooled to obtain the pre-oxidized cubic boron nitride powder.

5. The preparation method according to claim 4, characterized in that: The average particle size of the original cBN powder is 0.8-1.2 μm; the oxygen-containing atmosphere is an air atmosphere.

6. The preparation method according to claim 1, characterized in that: The average particle size of the LAS powder is 2.4-2.6 μm, the mass-to-volume ratio of the LAS powder to the aqueous dispersion containing the dispersant is 1 g: 1.8-2.2 mL, and the mass concentration of the dispersant in the aqueous dispersion is 0.45-0.55%.

7. The preparation method according to claim 1, characterized in that: The coating amount of the slurry on the carbon fiber cloth is 2100-2300 g / m. 2 The thickness of the prepreg is 0.9-1.1 mm.

8. The preparation method according to claim 1, characterized in that: The multilayer prepreg has 19-21 layers, and the volume fraction of carbon fiber cloth in the composite material is 38-42%.

9. The preparation method according to claim 1, characterized in that: The specific method for sintering is to raise the temperature to 1340-1360℃ at a rate of 4.8-5.2℃ / min, apply an axial pressure of 24-26MPa, and hold the temperature and pressure for 28-32 minutes.

10. The composite material prepared by the preparation method according to any one of claims 1-10.

Images