CVD protection method for graphite matrix special-shaped region

Abstract

The application belongs to the technical field of material preparation, and discloses a CVD protection method for a special-shaped area of a graphite matrix, which comprises the following steps: S1, filling slurry into the special-shaped area of the graphite matrix, wherein the slurry comprises expanded graphite powder, deionized water, polyethylene glycol and carbon nanotubes; S2, in an inert atmosphere, first heat preservation at 200 DEG C to 300 DEG C for 5 min to 15 min, and then heat preservation at 500 DEG C to 600 DEG C for 15 min to 25 min, so that the porosity of the slurry is kept at 40% to 60%; S3, using a CVD process to prepare a coating on the surface of the graphite matrix; and S4, removing the slurry and the coating at the special-shaped area of the graphite matrix. The application solves the problem that the coating material is not uniformly deposited in the CVD process of the special-shaped graphite part, meets the requirements of high-temperature stability, complex geometry adaptability, interface bonding reliability and process compatibility, and avoids the problems of coating precision out of control, material waste and product performance decline.

Description

Technical Field

[0001] This invention relates to a CVD protection method for irregular regions of a graphite matrix, belonging to the field of materials preparation technology. Background Technology

[0002] In high-end manufacturing, graphite materials are widely used due to their unique physicochemical properties. However, irregularly shaped graphite parts face special challenges in CVD coating processes. Irregularly shaped graphite parts typically refer to graphite components with complex geometric features (such as grooves, pores, curved surfaces, etc.). These special structures have key applications in semiconductors, aerospace, and nuclear industries. However, these irregularly shaped areas often lead to non-uniform deposition of coating materials during CVD processes. Reactive gases can seep into the grooves, forming undesirable coatings. This not only wastes expensive reactive gases but also results in discontinuous coatings on the workpiece surface, affecting the component's dimensional stability, high-temperature resistance, corrosion resistance, and mechanical properties.

[0003] Traditional methods for addressing coating penetration issues in irregularly shaped areas primarily include mechanical masking, resin filling, and pre-coating. Mechanical masking prevents gas from entering non-target areas through physical shielding, but it struggles to achieve complete coverage of complex three-dimensional structures and significantly increases process complexity. Resin filling (such as phenolic resin and epoxy resin) can fill irregularly shaped areas to some extent, but in the high-temperature environment of CVD processes, the resin carbonizes and decomposes, losing its sealing effect and even generating gaseous contamination of the deposition environment. Pre-coating techniques suffer from poor adhesion to the substrate interface and are prone to peeling, failing to meet the requirements of high-precision CVD processes.

[0004] Traditional protection methods cannot simultaneously meet the requirements of high-temperature stability, adaptability to complex geometries, reliability of interface bonding, and process compatibility, ultimately leading to problems such as loss of coating precision, material waste, and decreased product performance (such as dimensional deviations and reduced corrosion resistance). Summary of the Invention

[0005] This invention aims to provide a CVD protection method for irregularly shaped regions of a graphite substrate, solving the problem of non-uniform deposition of coating materials in irregularly shaped graphite parts during the CVD process, and meeting the requirements of high-temperature stability, adaptability to complex geometry, reliability of interface bonding, and process compatibility.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A CVD protection method for irregular regions in a graphite matrix includes the following steps:

[0008] S1. Fill the irregular region of the graphite matrix with slurry, wherein the slurry includes expanded graphite powder, deionized water, polyethylene glycol and carbon nanotubes;

[0009] S2. In an inert atmosphere, first keep the temperature at 200℃~300℃ for 5min~15min, then keep the temperature at 500℃~600℃ for 15min~25min, so that the porosity of the slurry is maintained at 40%~60%.

[0010] S3. Prepare a coating on the surface of a graphite substrate using CVD process;

[0011] S4. Remove the slurry and coating from the graphite substrate in irregularly shaped areas.

[0012] By employing a slurry composed of expanded graphite powder, deionized water, polyethylene glycol, and carbon nanotubes, the slurry achieves a certain viscosity and fluidity, enabling it to penetrate and completely fill irregularly shaped regions of the graphite matrix during pressure injection filling. Adding carbon nanotubes to the slurry enhances the interfacial bonding strength between the slurry and the graphite matrix, improving the slurry's mechanical stability during CVD. Low-temperature activation at 200℃–300℃ / 10min followed by high-temperature stabilization at 500℃–600℃ / 20min improves high-temperature stability and uniformity, preventing material splashing. Controlling the slurry porosity to maintain 40%–60% effectively blocks reactive gases (such as TiCl4) from the slurry's exterior during CVD, forming a protective layer for the internal graphite matrix. Pyrolysis byproducts (such as HCl) can escape from the pores, achieving directional gas sieving and preventing pressure buildup within the sealed layer, thus reducing slurry breakage. This protective method solves the problem of non-uniform deposition of coating materials in irregularly shaped graphite parts during CVD. It meets the requirements of high temperature stability, adaptability to complex geometry, reliability of interface bonding and process compatibility, and avoids problems such as loss of coating precision, material waste and deterioration of product performance.

[0013] Furthermore, in order to improve the filling effect and expansion uniformity of the slurry and enhance the interfacial bonding strength, in step S1: the particle size of the expanded graphite powder is 50μm to 200μm, the content of polyethylene glycol is 0.5wt% to 2wt%, and the mass ratio of carbon nanotubes is 5% to 10%.

[0014] Furthermore, in step S1: the polyethylene glycol specification is PEG-400.

[0015] Furthermore, in order to achieve complete filling without air bubbles, in step S1 the viscosity of the slurry is 500 cP to 2000 cP.

[0016] Furthermore, in order to overcome the filling resistance, avoid matrix cracking, and ensure filling uniformity, in step S1, the pressure of slurry filling is 0.1MPa to 0.5MPa.

[0017] Furthermore, in step S2: first, keep warm at 200℃~300℃ for 10 minutes, and then keep warm at 500℃~600℃ for 20 minutes.

[0018] Furthermore, the irregularly shaped area is a groove, hole, gap, or curved surface.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The CVD protection method for irregularly shaped regions of graphite substrates of the present invention solves the problem of non-uniform deposition of coating materials in irregularly shaped graphite parts during the CVD process. Compared with traditional protection methods, it simultaneously meets the requirements of high temperature stability, adaptability to complex geometry, reliability of interface bonding and process compatibility, and solves the problems of coating precision loss, material waste and product performance degradation. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the present invention.

[0022] In the diagram: 1. Graphite substrate; 2. Irregular area; 3. Slurry; 4. Coating. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings.

[0024] See Figure 1 This embodiment provides a CVD protection method for irregularly shaped regions of a graphite substrate. The method utilizes an expandable viscous slurry 3 to fill irregularly shaped regions 2 (such as grooves, pores, gaps, curved surfaces, etc.) of the graphite substrate 1 to prevent unintended penetration of the coating 4 during chemical vapor deposition (CVD). By precisely controlling the filling process and expansion parameters of the expandable viscous slurry 3, this method achieves perfect sealing of complex geometric regions of the graphite part, thereby ensuring that the CVD coating 4 is deposited only on a predetermined surface area, improving the precision, quality, and performance of the coating 4.

[0025] The method includes the following steps:

[0026] S1. Filling with Slurry 3: Prepare expandable viscous slurry 3 and inject it into the irregularly shaped regions 2 of the graphite matrix 1 under certain pressure. The formulation of slurry 3 is: expanded graphite powder with a particle size of 50μm to 200μm + deionized water + polyethylene glycol (PEG-400) with a content of 0.5wt% to 2wt% + carbon nanotubes with a mass ratio of 5% to 10%. The viscosity of slurry 3 is 500cP to 2000cP, and the filling pressure of slurry 3 is 0.1MPa to 0.5MPa. This allows for complete, bubble-free filling of the irregularly shaped regions 2 such as microgrooves / pores in the graphite matrix 1.

[0027] S2. Gradient Expansion Control: In an argon atmosphere, low-temperature activation is first performed, i.e., holding at 200℃~300℃ for 5min~15min to trigger partial expansion of expanded graphite (volume expansion of 50~100 times), initially forming a porous network; then high-temperature stabilization is performed, i.e., holding at 500℃~600℃ for 15min~25min to complete the final expansion (150-300 times), achieving densification of the pore structure and forming a rigid sealing layer.

[0028] S3. Pore Control of Slurry 3: By controlling the temperature and time parameters during the expansion process in step S2, the expansion rate and degree of the expandable viscous slurry 3 are adjusted, so that the porosity of slurry 3 is ultimately maintained at 40%–60%. Under this porosity, when slurry 3 undergoes CVD, reactive gases (such as TiCl4) can be blocked outside slurry 3, forming a protective layer for the internal graphite matrix 1, while pyrolysis byproducts (such as HCl) can escape from the pores, achieving the effect of directional gas sieving; at the same time, this structure can also avoid the accumulation of gas pressure inside the sealed layer, reducing the breakage rate of slurry 3.

[0029] S4, Coating 4 Preparation: Coating 4 is prepared on the surface of graphite substrate 1 using CVD process.

[0030] S5. Tooling cleaning: Remove the slurry 3 and coating 4 from the irregular area 2 of the graphite substrate 1.

[0031] In step S1 above, expanded graphite powder with a particle size of 50μm to 200μm can penetrate microgrooves with an aspect ratio greater than 5 (such as the 0.1mm trenches of a semiconductor graphite boat), while traditional fillers (such as resin) cannot enter such irregularly shaped regions 2. Deionized water can prevent oxidation reaction with graphite during the gradient expansion process from 200℃ to 600℃, thus avoiding the formation of carbonates that would clog the pores of the expanded graphite. Polyethylene glycol (PEG-400) is both a dispersant and a high-temperature binder. Its ether bonds can promote the sliding of graphite sheets during the 200℃ pre-expansion stage, and after carbonization at 600℃, it will help form a carbon network reinforcement structure. The viscosity of slurry 3 is controlled by adjusting the concentration of polyethylene glycol (PEG-400), and the filling pressure of slurry 3 is controlled by a pressure injection device. Pressure injection can ensure that slurry 3 completely fills irregularly shaped regions 2 without dead corners; by controlling the viscosity and filling pressure of slurry 3, perfect filling of structures with different aspect ratios can be achieved. Polyethylene glycol (PEG-400) acts as a viscosity solvent in slurry 3. Its addition amount or its ratio to expanded graphite powder determines the overall viscosity of slurry 3; the more PEG-400 added, the more viscous slurry 3 becomes. By adding 5%–10% carbon nanotubes to the expandable viscous slurry 3, interface strengthening can be achieved. The mechanism is as follows: at high temperatures, the nanomaterials form a three-dimensional interlocking structure with the graphite matrix 1, increasing the shear strength of the interface and preventing interfacial delamination caused by thermal stress during the CVD process.

[0032] In step S2 above, performing low-temperature activation followed by high-temperature stabilization avoids the instantaneous expansion that occurs in conventional processes using single-stage high-temperature expansion. This prevents slurry splashing, disordered pore structure, and the inability to achieve gas sieving, thus improving the uniformity of the filling structure. Low-temperature activation at 200℃–300℃ for 10 minutes initiates the decomposition of the intercalation compound and controls the expansion rate to ≤50 times / min, preventing splashing. High-temperature stabilization at 500℃–600℃ for 20 minutes promotes the densification and further expansion of the graphite sheets.

[0033] Example 1

[0034] The formulation of slurry 3 is: expanded graphite powder with a particle size of 50μm + deionized water + polyethylene glycol (PEG-400) with a content of 0.5wt% + carbon nanotubes with a mass ratio of 5%; the viscosity of slurry 3 is 500cP, and the filling pressure of slurry 3 is 0.1MPa.

[0035] Example 2

[0036] The formulation of slurry 3 is: expanded graphite powder with a particle size of 100μm + deionized water + polyethylene glycol (PEG-400) with a content of 1.0wt% + carbon nanotubes with a mass ratio of 8%; the viscosity of slurry 3 is 1000cP, and the filling pressure of slurry 3 is 0.3MPa.

[0037] Example 3

[0038] The formulation of slurry 3 is: expanded graphite powder with a particle size of 200μm + deionized water + polyethylene glycol (PEG-400) with a content of 2.0wt% + carbon nanotubes with a mass ratio of 10%; the viscosity of slurry 3 is 2000cP, and the filling pressure of slurry 3 is 0.5MPa.

[0039] Experiments show that Examples 1 to 3 all have excellent CVD protection effects.

[0040] The embodiments of the present invention have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention is not limited to the specific embodiments described above; these embodiments are merely illustrative and not limiting. Those skilled in the art, under the guidance of the present invention, can make many modifications without departing from the spirit and scope of the claims, and all such modifications fall within the scope of protection of the present invention.

Claims

1. A CVD protection method for irregularly shaped regions in a graphite matrix, characterized in that, Includes the following steps: S1. Fill the irregular region (2) of the graphite matrix (1) with slurry (3), wherein the slurry (3) includes expanded graphite powder, deionized water, polyethylene glycol and carbon nanotubes; S2. In an inert atmosphere, first keep it at 200℃~300℃ for 5min~15min, then keep it at 500℃~600℃ for 15min~25min, so that the porosity of the slurry (3) is maintained at 40%~60%; S3. A coating (4) is prepared on the surface of a graphite substrate (1) using a CVD process. S4. Remove the slurry (3) and coating (4) from the graphite substrate (1) in the irregular area (2); In step S1: the particle size of the expanded graphite powder is 50μm~200μm, the content of polyethylene glycol is 0.5wt%~2wt%, and the mass ratio of carbon nanotubes is 5%~10%.

2. The CVD protection method for irregular regions of a graphite matrix according to claim 1, characterized in that, In step S1: the polyethylene glycol specification is PEG-400.

3. The CVD protection method for irregular regions of a graphite matrix according to claim 1, characterized in that, In step S1: the viscosity of the slurry (3) is 500 cP to 2000 cP.

4. The CVD protection method for irregular regions of a graphite matrix according to claim 1, characterized in that, In step S1: the pressure of filling the slurry (3) is 0.1MPa~0.5MPa.

5. The CVD protection method for irregular regions of a graphite matrix according to claim 1, characterized in that, In step S2: First, keep warm at 200℃~300℃ for 10 minutes, then keep warm at 500℃~600℃ for 20 minutes.

6. The CVD protection method for irregular regions of a graphite matrix according to claim 1, characterized in that, The irregular region (2) is a groove, hole, gap, or curved surface.

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