Preparation method of high-density tantalum carbide coating
By using liquid-phase assisted TaC powder sintering and spray granulation processes to coat TaC powder with low-melting-point tantalum-containing powder, the problems of low density and insufficient bonding strength of TaC coatings were solved, thus achieving the growth requirements of high-quality SiC single crystals.
Patent Information
- Application Number
- CN202511601308.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-04
- Publication Date
- 2026-01-20
AI Technical Summary
Existing methods for preparing TaC coatings suffer from high energy consumption and low density, resulting in insufficient bonding strength between the coating and the substrate, which fails to meet the growth requirements of high-quality SiC single crystals.
A liquid-phase assisted TaC powder sintering method is adopted, in which a low-melting-point tantalum-containing material is coated around the TaC powder by spray granulation. The combination of spray granulation and sintering process alleviates stress concentration during sintering and improves coating density and bonding strength.
This improved the density of the tantalum carbide coating and its bonding strength with the substrate, meeting the requirements for the growth of high-quality SiC single crystals.
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Figure CN121362069A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of semiconductor processing, in particular to a preparation method of a high-density tantalum carbide coating. BACKGROUND
[0002] With the continuous iteration of technology, the first generation and the second generation of semiconductors are gradually replaced by the third generation of semiconductors. The third generation of semiconductors SiC and GaN are widely used in emerging fields such as rail transit, 5G communication and new energy vehicles. A high-quality SiC substrate needs a high-quality SiC single crystal to be processed by slicing, therefore, the quality of the SiC single crystal directly affects the use effect of the SiC substrate in related equipment such as power devices and high-frequency devices, therefore, improving the quality of the SiC single crystal has become the focus of industry research.
[0003] At present, in the growth process of the SiC single crystal, C particles and C inclusions cause various defects of the SiC substrate, and a high-temperature-resistant tantalum carbide (TaC) ceramic coating is usually used to improve the problem, therefore, improving the quality of the tantalum carbide coating is the key to ensuring the quality of the SiC single crystal. The existing method for preparing the TaC coating is usually a slurry sintering method, mainly adopting TaC powder as raw material to prepare the TaC coating through high-temperature sintering. Although the method can prepare the TaC coating, the sintering temperature is relatively high in the preparation process, the energy consumption is large, and the prepared TaC coating has a low density, so that the internal stress of the coating is large, the bonding strength between the coating and the base material is reduced, and the prepared TaC coating cannot better meet the growth demand of the high-quality SiC single crystal. SUMMARY
[0004] In view of the above problems in the prior art, the present application aims to provide a preparation method of a high-density tantalum carbide coating. The method adopts a liquid-assisted TaC powder sintering mode, and a low-melting-point tantalum-containing substance is wrapped around the TaC powder through spray granulation, so as to effectively alleviate the cracks caused by stress concentration between crystals due to the solid shrinkage of the TaC powder in the sintering process, improve the bonding strength between the coating and the base material, and also fill the pores at the TaC grain boundaries with liquid, so as to improve the density of the obtained TaC coating and better meet the growth demand of the high-quality SiC single crystal.
[0005] The specific technical scheme is as follows: A preparation method of a high-density tantalum carbide coating, comprising the following steps: Step S1, mixed slurry preparation; A predetermined amount of TaC powder and low-melting-point tantalum-containing powder is taken, and ammonium citrate, gum arabic and water are added and uniformly mixed to obtain a mixed slurry; Step S2, primary mixed powder preparation; The mixed slurry is granulated by spray granulation, and the TaC powder surface adsorbs low-melting-point tantalum-containing powder after drying to obtain a primary mixed powder; Step S3, secondary mixed powder preparation; The primary mixed powder is placed in a crucible made of tantalum paper and placed in a sintering furnace for sintering, and the secondary mixed powder of TaC powder surface wrapped with low-melting-point tantalum-containing powder is obtained after cooling; Step S4, secondary mixed powder screening; The secondary mixed powder obtained in step S3 is crushed and screened to obtain a tertiary mixed powder with a suitable particle size; Step S5, tantalum-containing suspension preparation; A predetermined amount of tertiary mixed powder is taken, and an organic binder and water are mixed uniformly to obtain a tantalum-containing suspension; Step S6, tantalum-containing pre-coating preparation; The tantalum-containing suspension is coated on the surface of the graphite substrate, and a tantalum-containing pre-coating is obtained after drying; Step S7, tantalum carbide pre-coating preparation; The tantalum-containing pre-coating is placed in a sintering furnace for sintering, and a tantalum carbide pre-coating is obtained after sintering and cooling.
[0006] The above method for preparing a high-density tantalum carbide coating, wherein in step S1, the component content of the TaC powder and the tantalum-containing powder is 1-5 mol and 1-30 mol, respectively, and the particle size range of the TaC powder and the tantalum-containing powder is 3-5 μm and 500 nm-3 μm, respectively.
[0007] The above method for preparing a high-density tantalum carbide coating, wherein in step S1, the mass percentage of ammonium citrate and gum arabic is 0.2-1% and 0.2-2%, respectively, and the rest is water.
[0008] The above method for preparing a high-density tantalum carbide coating, wherein the tantalum-containing powder includes one or a mixture of tantalum oxide, tantalum silicide, tantalum chloride, tantalum ethoxide solution, and tantalum powder.
[0009] The above method for preparing a high-density tantalum carbide coating, wherein the spray granulation is carried out in a spray granulator, and the inlet temperature of the spray granulator ranges from 150-200°C, the outlet temperature ranges from 50-100°C, and the feed flow rate ranges from 0.3-1 L / min.
[0010] In the above-mentioned method for preparing a high-density tantalum carbide coating, in step S3, when the crucible is placed in the sintering furnace for sintering, the sintering furnace is first evacuated, then filled with argon gas for gas protection, and heated to 1500-2000℃, with a sintering time range of 1-5h.
[0011] In the above-mentioned method for preparing a high-density tantalum carbide coating, the particle size range of the tertiary mixed powder obtained in step S4 is 5-10 μm.
[0012] In the above-mentioned method for preparing a high-density tantalum carbide coating, in step S5, the tertiary mixed powder is 30-40% by mass percentage, the organic binder is 0-1%, and the water is 60-70%. The mixing operation is carried out in a ball mill, and the ball milling is performed for 5-10 hours after adding the grinding beads.
[0013] In the above-mentioned method for preparing a high-density tantalum carbide coating, in step S6, when coating the tantalum-containing suspension onto the surface of the graphite substrate, the coating is carried out by brushing or spraying, and the coating thickness is 50-300 μm. The drying process is carried out in a drying oven, and the drying temperature range is 100-120℃, and the drying time range is 1-3h.
[0014] In the above-mentioned method for preparing a high-density tantalum carbide coating, in step S7, the sintering temperature range of the tantalum pre-coating is 1900-2300℃, the sintering pressure range is 50-200mbar, and the sintering time is 3-10h.
[0015] The positive effects of the above technical solution are: The above-mentioned method for preparing a high-density tantalum carbide coating involves first taking TaC powder and low-melting-point tantalum-containing powder, adding ammonium citrate, gum arabic, and water, mixing them evenly, and then granulating them using a spray granulator. After drying, a primary mixed powder containing low-melting-point tantalum-containing powder with adsorbed low-melting-point tantalum on the surface of tantalum carbide is obtained. The primary mixed powder is then sintered to obtain a secondary mixed powder with TaC powder coated with low-melting-point tantalum-containing powder. After crushing and sieving, a tertiary mixed powder with TaC powder coated with low-melting-point tantalum-containing powder of suitable particle size is obtained. Finally, the tertiary mixed powder is mixed with an organic binder and water. After mixing, the mixture is coated onto the surface of a graphite substrate and sintered to obtain a tantalum carbide pre-coating. This process not only uses liquid-phase assisted sintering of TaC powder, but also uses spray granulation and sintering to coat the TaC powder with a layer of low-melting-point tantalum-containing powder. This effectively alleviates the cracks and pores caused by stress concentration at grain boundaries due to the solid shrinkage of TaC powder during sintering, and improves the bonding strength between the coating and the substrate. At the same time, the liquid can fill the cracks and pores at the TaC grain boundaries, resulting in a denser tantalum carbide pre-coating that meets the growth requirements of high-quality SiC single crystals. Attached Figure Description
[0016] Figure 1 A flow chart of the preparation method of the high-density TaC coating according to the present application; Figure 2 A schematic diagram of the surface adsorption of the low-melting-point primary mixed powder containing tantalum on the TaC surface obtained in the preparation method of the high-density TaC coating according to the present application; Figure 3 A schematic diagram of the secondary mixed powder of the low-melting-point tantalum-containing powder wrapped on the surface of the TaC powder obtained in the preparation method of the high-density TaC coating according to the present application.
[0017] In the drawings: 1, TaC powder; 2, low-melting-point tantalum-containing powder. DETAILED DESCRIPTION
[0018] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the following examples are combined with the accompanying drawings to illustrate the present application. Figure 1 to the accompanying drawings Figure 3 The technical solutions provided by the present application are described in detail below, but the following content is not a limitation of the present application.
[0019] Figure 1 A flow chart of the preparation method of the high-density TaC coating according to the present application. As shown in the figure, Figure 1 The preparation method of the high-density TaC coating provided by the present embodiment includes the following steps: Step S1, preparation of mixed slurry; In the process of preparing the mixed slurry, a predetermined amount of TaC powder and low-melting-point tantalum-containing powder are first taken, and ammonium citrate, gum arabic and water are added, mixed uniformly, and the mixed slurry is obtained, which is convenient for subsequent spray granulation and also provides conditions for realizing liquid phase assisted sintering. It is worth pointing out that during the preparation of the mixed slurry, the mixing operation is realized by ball milling, and the grinding beads used for ball milling are preferably zirconia grinding beads, and the mixing is carried out on a ball mill, and the mixing time is 10-15h, so that the mixed slurry can be more uniform, which is convenient for subsequent spray granulation.
[0020] Specifically, during the preparation of the mixed slurry, the component contents of the selected TaC powder and the tantalum-containing powder are 1-5mol and 1-30mol, respectively, and the particle size ranges of the TaC powder and the tantalum-containing powder are 3-5μm and 500nm-3μm, respectively. In addition, the mass percentages of ammonium citrate and gum arabic are 0.2-1% and 0.2-2%, respectively, and the rest is water.
[0021] More specifically, the low-melting-point tantalum-containing powder includes, but is not limited to, one or a mixture of tantalum oxide, tantalum silicide, tantalum chloride, a tantalum ethoxide solution, and tantalum powder, and can provide a low-melting-point tantalum-containing powder, which provides a condition for subsequent adsorption on the surface of the TaC powder and wrapping on the surface of the TaC powder.
[0022] Step S2, preparation of a primary mixed powder; The mixture slurry obtained in step S1 is granulated by spray granulation, and after drying, a primary mixed powder of the TaC powder surface adsorbed with the low-melting-point tantalum-containing powder is obtained, which provides a condition for subsequent obtaining of the TaC powder wrapped with the low-melting-point tantalum powder. Figure 2 A schematic diagram of the primary mixed powder of the TaC powder surface adsorbed with the low-melting-point tantalum-containing powder obtained in the preparation method of the high-density TaC coating according to the present application is shown in FIG. 1. Figure 2 As shown in FIG. 1, the TaC powder 1 surface is uniformly adsorbed with a plurality of low-melting-point tantalum-containing powders 2, which provides a condition for subsequent wrapping of the low-melting-point tantalum-containing powder 2 on the surface of the TaC powder 1.
[0023] Specifically, the spray granulation process is carried out in a spray granulator, and the inlet temperature of the spray granulator ranges from 150 to 200°C, the outlet temperature ranges from 50 to 100°C, and the feed flow rate ranges from 0.3 to 1 L / min, so that the low-melting-point tantalum-containing powder adsorbed on the surface of the TaC powder in the obtained primary mixed powder is more uniform, and efficient granulation is achieved.
[0024] Step S3, preparation of a secondary mixed powder; The primary mixed powder obtained in step S2 is placed in a crucible made of tantalum paper and is integrally placed in a sintering furnace for sintering, and after cooling, a secondary mixed powder of the TaC powder surface wrapped with the low-melting-point tantalum-containing powder is obtained. At this time, by sintering the primary mixed powder in the sintering furnace through the crucible made of tantalum paper and then taking it out after cooling, the low-melting-point tantalum-containing powder wrapped TaC powder, i.e., the secondary mixed powder, can be obtained. In a liquid-phase-assisted sintering manner, the stress-induced crack porosity problem caused by the solid-phase reaction grain boundary shrinkage in the sintering process is alleviated. In addition, even if part of the crack porosity is generated, the liquid can fill the pores at the grain boundary, which provides a condition for subsequent obtaining of the high-density TaC coating. Figure 3 A schematic diagram of the secondary mixed powder of the TaC powder surface wrapped with the low-melting-point tantalum-containing powder obtained in the preparation method of the high-density TaC coating according to the present application is shown in FIG. 2. Figure 3 As shown in FIG. 2, the secondary mixed powder obtained after sintering and cooling has a structure of the TaC powder 1 surface wrapped with the low-melting-point tantalum-containing powder 2.
[0025] Specifically, when the crucible as a whole is put into the sintering furnace for sintering, the sintering furnace needs to be vacuumized first, and then filled with argon for gas protection to reduce external environmental interference. Moreover, the temperature of the sintering furnace is heated to 1500-2000℃, and sintering operation is performed for 1-5h to obtain the low-melting-point tantalum-containing powder-coated TaC powder.
[0026] Step S4, screening of the secondary mixed powder; The secondary mixed powder obtained in step S3 is crushed and screened to obtain a tertiary mixed powder with a particle size range of 5-10μm. At this time, the tertiary mixed powder is a low-melting-point tantalum-containing powder-coated TaC powder with a particle size meeting the set requirements.
[0027] Step S5, preparation of the tantalum-containing suspension; A predetermined amount of the tertiary mixed powder obtained in step S4 is taken, and an organic binder and water are added and uniformly mixed to obtain a tantalum-containing suspension. At this time, when taking each component, the tertiary mixed powder is 30-40% by mass percentage, the organic binder is 0-1%, and the water is 60-70%. Moreover, the mixing operation is realized by using a ball mill, that is, ball milling is performed after adding ball milling beads during mixing, and the ball milling time ranges from 5h to 10h, which provides conditions for subsequent smooth coating and stable adhesion to the surface of the substrate.
[0028] Step S6, preparation of the tantalum-containing pre-coating layer; The tantalum-containing suspension obtained in step S5 is coated on the surface of the graphite substrate by a method including but not limited to brushing and spraying, and the coating thickness is controlled to be 50-300μm. In addition, after coating is completed, it needs to be transferred to a drying box for drying, and the temperature during drying is preferably in the range of 100-120℃, and the drying time is 1-3h. After drying, a tantalum-containing pre-coating layer is obtained; Step S7, preparation of the tantalum carbide pre-coating layer; The tantalum-containing pre-coating layer obtained in step S6 is put into a sintering furnace for sintering, and the sintering temperature is preferably in the range of 1900-2300℃, the sintering pressure is in the range of 50-200mbar, and the sintering time is 3-10h. After sintering and cooling, a tantalum carbide pre-coating layer is obtained, which has higher compactness and is more uniform, and is beneficial to high-quality SiC single crystal growth.
[0029] The preparation method of the high-density tantalum carbide coating provided by the embodiment comprises the following steps: S1, mixing slurry preparation; S2, primary mixed powder preparation; S3, secondary mixed powder preparation; S4, secondary mixed powder screening; S5, tantalum-containing suspension preparation; S6, tantalum-containing pre-coating preparation; and S7, tantalum carbide pre-coating preparation. The primary mixed powder of low-melting-point tantalum-containing powder adsorbed on the surface of the TaC powder is obtained by adding ammonium citrate, gum arabic and water into the TaC powder and the low-melting-point tantalum-containing powder, mixing uniformly, and then using a spray granulator to granulate. The secondary mixed powder of the TaC powder wrapped with the low-melting-point tantalum-containing powder is obtained by sintering. The tertiary mixed powder with a proper particle size is obtained after crushing and screening. The tertiary mixed powder is mixed with an organic binder and water, and then coated on the surface of a graphite substrate. After drying and sintering, the tantalum carbide pre-coating is obtained. The liquid-phase assisted sintering of the TaC powder is realized. A layer of low-melting-point tantalum-containing powder is wrapped around the TaC powder by means of spray granulation and sintering. The cracks and pores caused by stress concentration between the grain boundaries due to the solid shrinkage of the TaC powder in the sintering process are effectively relieved. The bonding degree between the coating and the substrate is better. The liquid is filled into the cracks and pores at the grain boundaries of the TaC, which further improves the density of the tantalum carbide pre-coating and better meets the growth requirements of high-quality SiC single crystals.
[0030] The above merely describes preferred embodiments of the present application, but does not limit the embodiments and protection scope of the present application. Those skilled in the art should realize that equivalent replacements and obvious changes made according to the content of the present application should be included in the protection scope of the present application.
Claims
1. A method for preparing a high-density tantalum carbide coating, characterized in that, It includes the following steps: Step S1, preparation of the mixed slurry; Take a predetermined amount of TaC powder and low-melting-point tantalum-containing powder, add ammonium citrate, gum arabic and water, mix evenly to obtain a slurry; Step S2, preparation of primary mixed powder; The mixed slurry was granulated by spray granulation and dried to obtain a primary mixed powder containing tantalum powder with low melting point adsorbed on the surface of TaC powder. Step S3, preparation of secondary mixed powder; The primary mixed powder was placed in a crucible made of tantalum paper and sintered in a sintering furnace. After cooling, a secondary mixed powder containing low-melting-point tantalum powder was obtained with TaC powder coated on the surface. Step S4, secondary mixed powder sieving; The secondary mixed powder obtained in step S3 is crushed and sieved to obtain a tertiary mixed powder with a suitable particle size. Step S5: Preparation of tantalum-containing suspension; Take a predetermined amount of the three-stage mixed powder, add an organic binder and water, mix evenly to obtain a tantalum-containing suspension; Step S6: Preparation of tantalum pre-coating; A tantalum-containing suspension is coated onto the surface of a graphite substrate, and after drying, a tantalum-containing pre-coating is obtained. Step S7, preparation of tantalum carbide pre-coating; The tantalum pre-coating is placed in a sintering furnace for sintering, and after sintering and cooling, tantalum carbide pre-coating is obtained.
2. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, In step S1, the component contents of TaC powder and tantalum-containing powder are 1-5 mol and 1-30 mol, respectively, and the particle size ranges of TaC powder and tantalum-containing powder are 3-5 μm and 500 nm-3 μm, respectively.
3. The method for preparing a high-density tantalum carbide coating according to claim 2, characterized in that, In step S1, by mass percentage, ammonium citrate and gum arabic are 0.2-1% and 0.2-2% respectively, with the remainder being water.
4. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, The tantalum-containing powder includes one or a mixture of tantalum oxide, tantalum silicide, tantalum chloride, tantalum ethoxide solution, and tantalum powder.
5. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, The spray granulation is carried out in a spray granulator, and the inlet temperature range of the spray granulator is 150-200℃, the outlet temperature range is 50-100℃, and the feed flow rate range is 0.3-1L / min.
6. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, In step S3, when the crucible is placed in the sintering furnace for sintering, the sintering furnace is first evacuated, then filled with argon gas for gas protection, and heated to 1500-2000℃, with a sintering time range of 1-5h.
7. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, The particle size range of the three-stage mixed powder obtained in step S4 is 5-10 μm.
8. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, In step S5, the tertiary mixed powder comprises 30-40% by mass percentage, the organic binder comprises 0-1%, and the water comprises 60-70%. The mixing operation is carried out in a ball mill, and the ball milling is performed for 5-10 hours after adding the grinding beads.
9. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, In step S6, when coating the tantalum suspension onto the graphite substrate surface, the coating is carried out by brushing or spraying, and the coating thickness is 50-300μm. The drying process is carried out in a drying oven, and the drying temperature range is 100-120℃, and the drying time range is 1-3h.
10. The method for preparing a high-density tantalum carbide coating according to claim 1, characterized in that, In step S7, the sintering temperature range of the tantalum pre-coating is 1900-2300℃, the sintering pressure range is 50-200mb, and the sintering time is 3-10h.