A slurry and sintering method for making a dense tantalum carbide coating

Abstract

The application provides a slurry and a sintering method for preparing a dense tantalum carbide coating, wherein the slurry is prepared by mixing tantalum carbide powder, a sintering aid, a binder and an organic solvent according to certain mass fractions, and then mixing the suspension by a ball mill to form a suspension; the sintering method is to uniformly coat the slurry on the surface of a graphite piece, dry and solidify the coating, and finally sinter the graphite piece coated with the coating. The application aims to use tantalum carbide powder and a sintering aid as the main body, and through an optimized mixed solvent, a high-quality tantalum carbide coating slurry with good suspension stability, high solid content, strong fluidity, high coating film quality and no cracking after sintering is prepared. The slurry and the sintering process are simpler, and the slurry does not involve chemical reaction in the subsequent sintering process, so that the by-products generated in the chemical reaction process can be avoided, and the prepared tantalum carbide coating has higher purity and a dense and flat film crystal.

Description

Technical Field

[0001] This invention relates to the field of high-temperature and corrosion-resistant ceramic coating technology, specifically to a slurry and sintering method for preparing a dense tantalum carbide coating. Background Technology

[0002] Tantalum carbide ceramics have a high melting point of 3880℃, high hardness, high thermal conductivity, high flexural strength, and low coefficient of thermal expansion. They also exhibit excellent thermochemical stability and superior physical properties, demonstrating good chemical and mechanical compatibility with graphite and C / C composites. Therefore, tantalum carbide coatings are widely used in aerospace thermal protection, single crystal growth, energy electronics, and medical devices. Tantalum carbide-coated graphite exhibits better chemical corrosion resistance than bare graphite or SiC-coated graphite, can be used stably at 2600℃, and does not react with many metallic elements. It is the best-performing coating for third-generation semiconductor single crystal growth and wafer etching, significantly improving temperature and impurity control during the process and enabling the fabrication of high-quality silicon carbide wafers and related epitaxial wafers. It is particularly suitable for growing GaN or AlN single crystals in MOCVD equipment and SiC single crystals in PVT equipment, resulting in a significant improvement in the quality of the grown single crystals.

[0003] Currently, chemical vapor deposition (CVD) is the most common method used to prepare tantalum carbide coatings. Its disadvantages are: low coating deposition rate, long deposition cycle, high equipment cost, and the coating is prone to cracks and pores. This fatal defect leads to low reliability in its application, thus losing its protective effect on the crystal. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a method to overcome the shortcomings of CVD method for preparing tantalum carbide coatings by directly using slurry sintering method with tantalum carbide powder as the main raw material to prepare a tantalum carbide coating on a substrate such as graphite; and the slurry sintering method for preparing tantalum carbide coatings has significant advantages such as low cost, simple process operation and short preparation cycle.

[0005] This application aims to address, to some extent, the problems in the preparation and sintering process of tantalum carbide coating slurry.

[0006] The slurry preparation method for preparing dense tantalum carbide coatings proposed in this application uses simple and readily available raw materials, and the prepared slurry has good suspension stability, good fluidity, and is easy to spray, resulting in high-quality coating film.

[0007] To achieve the above objectives, the present invention provides a slurry and sintering method for preparing a dense tantalum carbide coating.

[0008] The first aspect of this application provides a slurry for preparing a dense tantalum carbide coating, comprising a volatile mixed organic solvent, tantalum carbide solid powder particles insoluble in the solvent, sintering aid solid powder particles insoluble in the solvent, and a binder soluble in the solvent, mixed in a certain mass fraction, and ball milling the mixed suspension of the raw material components to form a uniformly mixed suspension.

[0009] In any embodiment, the mixed organic solvent is a volatile mixed organic solvent, which is an alcohol or ketone solvent, and is an organic solvent that has good wettability to tantalum carbide solid powder particles and can be suspended therein for a long time without settling.

[0010] In any embodiment, the mixed organic solvent is at least two of the alcohol and ketone organic solvents such as ethanol, cyclohexanol, glycerol, acetone, and cyclohexanone, preferably two to five.

[0011] In any embodiment, the mixed organic solvent is composed of several organic solvents with different boiling points mixed in a certain proportion, namely, low-boiling-point solvent, medium-boiling-point solvent and high-boiling-point solvent; wherein, the low-boiling-point solvent has a boiling point of less than 100°C, the medium-boiling-point solvent has a boiling point of 100-200°C, and the high-boiling-point solvent has a boiling point of greater than 200°C.

[0012] In any embodiment, the high-boiling-point organic solvent in the mixed solvent accounts for more than 10 wt% of the total slurry.

[0013] In any embodiment, the tantalum carbide solid powder particles have an average particle size of 1μm-10μm and a purity greater than 99%.

[0014] In any embodiment, the sintering aid is one or more of a reducing additive and a second-phase additive.

[0015] In any embodiment, the reducing additive is TiB2, B4C, etc., and the second phase additive is SiC, WC, etc.

[0016] In any embodiment, the content of the sintering aid is 1-5 wt% of the tantalum carbide solid powder.

[0017] In any embodiment, the adhesive is an organic soluble adhesive, which is one or more of vinyl adhesives, acrylic adhesives, or resin adhesives.

[0018] In any embodiment, the mixed organic solvent accounts for 20-50 wt% of the total slurry by mass. The tantalum carbide solid powder particles account for 50-80 wt% of the total slurry by mass; the sintering aid solid powder particles account for 0.5-3 wt% of the total slurry by mass; and the binder accounts for 0.5-1 wt% of the total slurry by mass.

[0019] In any embodiment, after the slurry suspension is shaken and mixed evenly and left to stand for 2-4 hours, no obvious solid-liquid separation phenomenon occurs between the solid powder particles and the liquid mixed organic solvent; the bulk density of the powder after the slurry is dried can reach more than 70%.

[0020] The second aspect of this application provides a sintering method for preparing a dense tantalum carbide coating, comprising the following steps: 1) uniformly coating a slurry onto a graphite surface at room temperature; 2) placing the coated graphite part in a protective gas environment at 200-300°C for 1 hour to dry and cure; 3) placing the dried and cured tantalum carbide coated graphite part in a protective gas or vacuum environment at 2000-2500°C for 2-3 hours to sinter.

[0021] In any embodiment, the coating process for a single application does not exceed 2 minutes. After a single application, the coating is allowed to stand and dry. This process is repeated 3-5 times to obtain a tantalum carbide coating with a thickness of 50-100 μm.

[0022] In any embodiment, the heating rate of the drying and curing stage is 3-8℃ / min; the heating rate of the sintering process is 5-15℃ / min, and the high temperature maintenance time is 2-3 hours.

[0023] The present invention has the following advantages:

[0024] The tantalum carbide coating slurry formulated in this invention exhibits good suspension stability, is not prone to deposition, has good fluidity for easy coating, and produces a high-quality coating film. The coating prepared by spraying this slurry shows good adhesion to the substrate after drying, without cracking or peeling. The coating prepared by this sintering process shows strong bonding to the graphite substrate after high-temperature sintering, and electron microscopy reveals a high density morphology. The tantalum carbide coating slurry preparation and sintering process of this invention are simple and can be used to prepare a tantalum carbide coating with high density, high bonding strength, and suitable thickness. Attached Figure Description

[0025] Figure 1 This is a physical image of a slurry used to prepare a dense tantalum carbide coating according to this application.

[0026] Figure 2 This is a photograph of the tantalum carbide coating applied to the surface of a graphite material and then dried, as per this application.

[0027] Figure 3 This is a scanning electron microscope image of the tantalum carbide coating surface after it has been sprayed with tantalum carbide slurry and dried on the graphite material surface according to this application.

[0028] Figure 4 This image shows a tantalum carbide coating after sintering at 2400°C in an environment with argon protective gas, according to a sintering method for preparing a dense tantalum carbide coating as described in this application.

[0029] Figure 5 This is a scanning electron microscope image of the tantalum carbide coating surface after sintering at 2400°C in an environment with argon protective gas, according to a sintering method for preparing a dense tantalum carbide coating of this application. Detailed Implementation

[0030] The following detailed description, with appropriate reference to the accompanying drawings, discloses an embodiment of a slurry and sintering method for preparing a dense tantalum carbide coating according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0031] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0034] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0036] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0037] The key to preparing tantalum carbide coatings using the slurry sintering method lies in the slurry preparation and sintering process, which directly affect the performance of the sintered tantalum carbide coating. The solvent composition used in the slurry is crucial in limiting its dispersibility and solid content. Existing solvent systems cannot achieve slurries with good suspension stability and high solid content, and therefore cannot produce tantalum carbide coating films with high packing density, smooth texture, and strong adhesion after sintering. Currently, there is very little research on the specific details of slurry preparation and sintering processes for preparing tantalum carbide coatings using the slurry sintering method. Therefore, this invention focuses on how the specific details of the tantalum carbide coating slurry and sintering process improve product performance.

[0038] Reference Appendix Figure 1-3A slurry for preparing a dense tantalum carbide coating comprises a volatile mixed organic solvent, tantalum carbide solid powder particles insoluble in the solvent, sintering aid solid powder particles insoluble in the solvent, and a binder soluble in the solvent, wherein the mixed suspension of the raw material components is ball-milled to form a uniformly mixed suspension.

[0039] Solvents, as an important component of slurries, impart fluidity to the slurry, allowing the powder to be uniformly suspended in the liquid. They also uniformly disperse various additive components, forming a stable and homogeneous suspension mixture with high solids content. Therefore, the main functions of solvents are: 1) dissolving binders, plasticizers, and other additives; 2) ensuring uniform dispersion of ceramic powder particles; 3) providing the slurry with suitable viscosity and good fluidity; and 4) allowing for drying and volatility reduction.

[0040] In any embodiment, the organic solvent is an alcohol, ketone, or other organic solvent that provides good wettability to tantalum carbide solid powder particles and allows them to remain suspended for a relatively long time without settling. Preferably, it is an organic solvent capable of keeping tantalum carbide solid powder particles suspended for 1-5 hours without settling, such as ethanol, cyclohexanol, glycerol, acetone, and cyclohexanone. The longer the suspension time of tantalum carbide solid powder particles in the organic solvent, the higher the solid content of the coating slurry, the higher the bulk density of the tantalum carbide coating powder after spraying, and the higher the density after high-temperature sintering. Therefore, selecting an organic solvent with a long suspension time for tantalum carbide solid powder particles is essential.

[0041] In any embodiment, the organic solvent is a mixture of 2-5 organic solvents with different boiling points in a certain proportion. A single organic solvent cannot meet the requirements of the subsequent gradient temperature drying process, and using a single organic solvent easily leads to stress cracking and peeling of the slurry surface. Therefore, this application employs a ternary or multi-element mixed solvent combination. Using mixed organic solvents with different boiling points can control the drying rate of the wetted tantalum carbide coating, while reducing drying stress during the coating drying process and preventing coating cracking or peeling during slurry drying. Based on their boiling points, organic solvents can be classified as low-boiling-point solvents, medium-boiling-point solvents, and high-boiling-point solvents. Low-boiling-point solvents have a boiling point less than 100°C, medium-boiling-point solvents have a boiling point of 100-200°C, and high-boiling-point solvents have a boiling point greater than 200°C. The high-boiling-point organic solvent in the mixed solvent must account for more than 10 wt% of the total slurry mass to prevent coating cracking or peeling during the subsequent drying process.

[0042] In some embodiments, the average particle size of the tantalum carbide solid powder is 1μm-10μm, and the purity is greater than 99%. Experimental studies on the entire scheme have found that the average particle size of the tantalum carbide solid powder should not exceed 10μm. According to the principle of powder sintering densification, on the one hand, the larger the powder particle size, the larger the porosity between powder particles, which is not conducive to improving the density of the coating after sintering; on the other hand, the larger the powder particle size, the higher the diffusion activation energy required for the powder, which reduces the material diffusion and grain boundary diffusion on the surface of the powder particles, thereby reducing the density of the coating. At the same time, the average particle size of the tantalum carbide solid powder should not be less than 1μm. If the powder particle size is too small, abnormal or rapid grain growth will occur during the high-temperature sintering densification process, which will prevent the coating stress from being fully released, resulting in peeling, flaking, and cracking.

[0043] In any embodiment, the sintering aid is one or more of a reducing additive and a second-phase additive. The reducing additive is TiB2, B4C, etc., and the second-phase additive is SiC, WC, etc. The reducing additive, such as TiB2, B4C, etc., removes oxygen from the slurry during high-temperature sintering through a reduction reaction, thereby increasing the density of the sintered coating. The second-phase additive, such as SiC, WC, etc., can lower the temperature required for sintering densification and can also inhibit excessive grain growth in the later stages of sintering, thus increasing the density of the sintered coating.

[0044] In any embodiment, the content of the sintering aid is 1-5 wt% of the tantalum carbide powder by mass. The content of the sintering aid is required to be no less than 1 wt% of the tantalum carbide powder by mass; below this content, the coating density is not significantly improved. Simultaneously, the content of the sintering aid is required to not exceed 5 wt% of the tantalum carbide powder by mass; excessively high content will decrease the bonding strength between the tantalum carbide coating and graphite, as well as its thermal shock resistance and corrosion resistance.

[0045] In any embodiment, the binder is an organic soluble binder. The binder has the greatest impact on the strength, plasticity, flexibility, and smoothness of the slurry; its type and content determine the strength and density of the coating. The selected binder should have the following characteristics: 1) it does not affect solvent evaporation and does not generate bubbles; 2) it can prevent particle sedimentation; 3) it is easy to burn off, leaving no residue; 4) it does not adhere to the substrate. The organic soluble binder is one or more of vinyl-based binders, acrylic binders, or resin-based binders. Vinyl-based binders include polyvinyl alcohol (PVA) and polyvinyl butyral (PVB). Acrylic binders include polyacrylic acid (PAA), polymethyl methacrylate (PMMA), and polyethyl methacrylate (PEMA). Resin-based binders include epoxy acrylate resin (EA) and phenolic resin (PF). The binder is an important additive in tantalum carbide slurry, encapsulating the powder and resulting in smaller particle spacing in the tantalum carbide powder.

[0046] In any embodiment, the binder content is 0.5-1 wt% of the total slurry mass fraction. The binder content should not be too low, as this will result in poor bonding between powder particles, low powder bulk density after spraying, and hinder the sintering and densification of the coating. Similarly, the binder content should not be too high, as this will make the slurry viscous and less fluid, which is not conducive to spraying and reduces the uniformity of the coating after spraying.

[0047] In any embodiment, the mixed organic solvent accounts for 20-50 wt% of the total slurry by mass. The tantalum carbide solid powder particles account for 50-80 wt% of the total slurry by mass; the sintering aid solid powder particles account for 0.5-3 wt% of the total slurry by mass; and the binder accounts for 0.5-1 wt% of the total slurry by mass.

[0048] In any embodiment, after the slurry suspension is shaken and mixed evenly and left to stand for 2-4 hours, no obvious solid-liquid separation phenomenon occurs between the solid powder particles and the liquid mixed organic solvent; the bulk density of the powder after the slurry is dried can reach more than 70%.

[0049] Reference Appendix Figure 1-5 A sintering method for preparing a dense tantalum carbide coating includes the following steps: 1) uniformly coating a slurry onto a graphite surface at room temperature; 2) placing the coated graphite part in a protective gas environment at 200-300°C for 1 hour to dry and cure; 3) placing the dried and cured tantalum carbide coated graphite part in a protective gas or vacuum environment at 2000-2500°C for 2-3 hours to sinter.

[0050] The slurry is uniformly coated onto the graphite surface at room temperature (approximately 25°C) using methods including but not limited to spraying, dip coating, scraping, and spin coating. Drying and curing remove organic solvents and binders. The drying and curing temperature must be >200°C; otherwise, high-boiling-point organic solvents cannot be fully evaporated and removed. The drying and curing temperature must be <300°C; otherwise, high-boiling-point organic solvents may boil, compromising the uniformity and smoothness of the coating surface. Sintering for 2-3 hours allows the tantalum carbide solid powder to form a dense tantalum carbide coating under high-temperature diffusion. The sintering temperature must be 2000-2500°C. Sintering below 2000°C results in low sintering driving energy and low coating density observed under electron microscopy. Sintering above 2500°C causes the coating surface to blacken, and XRD analysis reveals carbon peaks in the blackened areas, indicating carbonization of the coating.

[0051] In any embodiment, the coating process for a single application does not exceed 2 minutes. After a single application, the coating is allowed to stand and dry. This process is repeated 3-5 times to obtain a tantalum carbide coating with a thickness of 50-100 μm.

[0052] Each coating process should not exceed 2 minutes; after each coating, the coating should be allowed to stand and dry to evaporate organic solvents and avoid uneven coating caused by liquid surface tension.

[0053] In any embodiment, the heating rate of the drying and curing stage is 3-8℃ / min; the heating rate of the sintering process is 5-15℃ / min, and the high temperature maintenance time is 2-3 hours.

[0054] During the drying and curing stage, a slow temperature increase (3-8℃ / min) is required to gradually release coating stress and prevent cracking and peeling. Simultaneously, it is crucial to prevent the organic solvents within the coating from reaching their boiling point too quickly, which could cause raised dots on the coating surface. The sintering atmosphere should be provided with a protective gas such as argon or a vacuum environment. The sintering process requires a heating rate of 5-15℃ / min to slowly release coating stress and prevent cracking or peeling due to excessively rapid heating.

[0055] Example

[0056] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0057] Example 1:

[0058] Weigh 5g of tantalum carbide powder with a particle size of 1-3μm and a purity of 99.5%; weigh 0.2g of WC powder as a second-phase sintering aid; weigh 0.05g of PVB powder as a binder; uniformly mix ethanol, cyclohexanol, and glycerol in a volume ratio of 2:2:1, and measure 4.75g as the organic solvent; mix the above four raw materials together and ball-mill to form a stable, free-flowing tantalum carbide slurry. Apply the slurry uniformly to the graphite surface using a spraying method. After each spraying cycle, allow the coating to stand and dry for a period of time, repeating this process three times. After spraying, place the graphite part coated with tantalum carbide in an environment of 300℃ with a protective gas such as argon to dry and cure for 1 hour, removing the organic solvent and binder. The heating rate during the drying and curing stage is 5℃ / min. Finally, place the dried and cured tantalum carbide-coated graphite part in a vacuum environment of 2400℃ for sintering for 2 hours, with a heating rate of 10℃ / min.

[0059] Example 2:

[0060] Weigh 5g of tantalum carbide powder with a particle size of 1-3μm and a purity of 99.5%; weigh 0.2g of B4C powder as a reducing sintering aid; weigh 0.05g of phenolic resin powder as a binder; uniformly mix ethylene glycol, cyclohexanone, and glycerol in a volume ratio of 2:2:1, and measure 4.75g as the organic solvent; mix the above four raw materials together and ball-mill to form a stable, free-flowing tantalum carbide slurry. Apply the slurry uniformly to the graphite surface using a spraying method. After each spraying cycle, allow the coating to stand and dry for a period of time, repeating this process three times. After spraying, place the graphite part coated with tantalum carbide in an environment at 300℃ with a protective gas such as argon to dry and cure for 1 hour, removing the organic solvent and binder. The heating rate during the drying and curing stage is 5℃ / min. Finally, the dried and cured tantalum carbide coated graphite parts were placed in a vacuum environment at 2400℃ for 2 hours for sintering, with a heating rate of 10℃ / min.

[0061] Example 3:

[0062] Weigh 5g of tantalum carbide powder with a particle size of 1-3μm and a purity of 99.5%; weigh 0.2g of TiB2 powder as a second-phase sintering aid; weigh 0.05g of PAA powder as a binder; uniformly mix ethanol, cyclohexanone, and glycerol in a volume ratio of 2:2:1, and measure 4.75g as the organic solvent; mix the above four raw materials together and ball-mill to form a stable, free-flowing tantalum carbide slurry. Apply the slurry uniformly to the graphite surface using a spraying method. After each spraying cycle, allow the coating to stand and dry for a period of time, repeating this process three times. After spraying, place the graphite part coated with tantalum carbide in an environment of 300℃ with a protective gas such as argon to dry and cure for 1 hour, removing the organic solvent and binder. The heating rate during the drying and curing stage is 5℃ / min. Finally, place the dried and cured tantalum carbide-coated graphite part in a vacuum environment of 2400℃ for sintering for 2 hours, with a heating rate of 10℃ / min.

[0063] Figure 1 The photographs of the slurries prepared in Example 1 (1#), Example 2 (2#), and Example 3 (3#) are shown from left to right, showing that the slurries are uniformly dispersed in the solvent. Figure 2 The photo shows the graphite surface after the slurry was sprayed onto the surface of the graphite material in Example 1 and dried. It can be seen that the coating on the graphite surface is evenly distributed and the surface is flat, smooth and free of voids. Figure 3 As shown in Example 1, a slurry was sprayed onto the surface of a graphite material. After drying, the surface scanning electron microscope image shows that the solid powder of the slurry is densely and uniformly distributed in the microstructure, with no obvious macroscopic voids. Figure 4 The photo shows the actual product of the first example, after the slurry was sprayed onto the surface of the graphite material and sintered at 2400℃ for 2 hours. It can be seen that the surface of the sample after sintering is smooth, the texture is uniform, there are no defects that can be distinguished by the naked eye, and the uniform color indicates that the thickness is uniform. Figure 5 The electron microscope image shown is a physical image of the slurry sprayed onto the surface of a graphite material and sintered at 2400°C for 2 hours in Example 1. It can be seen that the sintered coating is uniform and dense, and the surface is composed of densely stacked large tantalum carbide grains, which confirms that the slurry and sintering method of the present invention can prepare high-quality tantalum carbide coatings.

[0064] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A slurry for preparing a dense tantalum carbide coating, characterized in that, The mixture of volatile organic solvents, tantalum carbide solid powder particles insoluble in solvents, sintering aid solid powder particles insoluble in solvents, and binders soluble in solvents is ball-milled to form a uniformly mixed suspension. The sintering aid is one or more of a reducing additive and a second-phase additive; the reducing additive is TiB2 or B4C, and the second-phase additive is SiC or WC; the content of the sintering aid is 1wt%-5wt% of the mass fraction of tantalum carbide powder. The binder is an organic soluble binder, which is one of vinyl-based, acrylic-based, or resin-based binders; the content of the binder is 0.5-1 wt% of the total slurry. The mixed organic solvent is a volatile mixed organic solvent, which is an alcohol or ketone solvent, and has good wettability to tantalum carbide solid powder particles, and can be suspended in it for a long time without settling; the mixed organic solvent is at least two of ethanol, cyclohexanol, glycerol, acetone, and cyclohexanone. The mixed organic solvent is composed of several organic solvents with different boiling points mixed in a certain proportion, namely, low-boiling-point solvent, medium-boiling-point solvent and high-boiling-point solvent; wherein, the low-boiling-point solvent has a boiling point of less than 100℃, the medium-boiling-point solvent has a boiling point of 100-200℃, and the high-boiling-point solvent has a boiling point of greater than 200℃; the high-boiling-point organic solvent in the mixed organic solvent accounts for more than 10 wt% of the total slurry.

2. The slurry according to claim 1, characterized in that, The tantalum carbide solid powder particles have an average particle size of 1μm-10μm and a purity greater than 99%.

3. The slurry according to claim 1, characterized in that, After the slurry suspension is shaken, mixed evenly, and left to stand for several hours, no obvious solid-liquid separation phenomenon occurs between the solid powder particles and the liquid mixed organic solvent; the bulk density of the powder after the slurry is dried can reach more than 70%.

4. The slurry according to claim 1, characterized in that, The tantalum carbide solid powder particles account for 50-80 wt% of the total slurry; the sintering aid solid powder particles account for 0.5-3 wt% of the total slurry; the binder solid powder particles account for 0.5-1 wt% of the total slurry; and the mixed organic solvent accounts for 20-50 wt% of the total slurry.

5. A sintering method for preparing a dense tantalum carbide coating, using the slurry according to any one of claims 1-4, comprising the following steps: 1) uniformly coating the slurry onto a graphite surface at room temperature; 2) placing the coated graphite part in a protective gas environment at 200-300°C for drying and curing for 1 hour; 3) placing the dried and cured tantalum carbide coated graphite part in a protective gas or vacuum environment at 2000-2500°C for sintering for 2-3 hours.

6. The sintering method according to claim 5, characterized in that, The coating process is completed in a single application that takes no more than 2 minutes. After each application, the coating is allowed to stand and dry. This process is repeated 3-5 times to obtain a tantalum carbide coating with a thickness of 50-100 μm.

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