Safe and efficient preparation method of hafnium carbide coating

Abstract

The application discloses a safe and efficient preparation method of hafnium carbide coating, adopts a laser chemical vapor deposition method, and comprises the following steps: substrate cleaning, equipment connection, substrate placement, equipment vacuumizing, raw material tank heating, reaction environment construction, reaction, laser irradiation on the substrate to start the substrate surface temperature rise to the reaction temperature, then reaction with the precursor gas and the reaction gas to start the deposition reaction, and post-processing, taking out the substrate, and covering the hafnium carbide coating on the substrate surface. The safe and efficient preparation method of the hafnium carbide coating has the advantages that the hafnium carbide coating obtained by the method has extremely high stability, excellent heat shock resistance and ablation resistance, and a high deposition rate, and the required hafnium carbide coating can be obtained only by short-time deposition, the method is convenient to use, short in time consumption, and can effectively reduce resource loss.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically, it relates to a safe and efficient method for preparing hafnium carbide coatings. Background Technology

[0002] Carbon / carbon composites are considered one of the most promising thermal structural materials due to their excellent high-temperature mechanical properties, such as low density, low coefficient of thermal expansion, good thermal shock resistance, and good heat resistance. However, carbon / carbon composites deteriorate severely in oxygen-containing ablation environments, which limits their application in high-temperature structural components. Preparing ablation-resistant coatings is an effective way to address this problem.

[0003] Hafnium carbide possesses advantages such as a high melting point (3890℃), low vapor pressure, extremely high phase stability, good mechanical properties, and superior resistance to thermal shock and ablation. It is widely considered a suitable candidate material for ablation-resistant coatings on carbon / carbon composites. Hafnium carbide coating preparation techniques include plasma spraying, chemical vapor deposition (CVD), hot pressing, and embedding. Among these, CVD has attracted significant attention due to its low deposition temperature, good uniformity, and high density, and is the primary method for preparing high-quality hafnium carbide coatings.

[0004] To date, the preparation of hafnium carbide coatings using chemical vapor deposition (CVD) primarily utilizes hafnium chloride as a precursor. The use of small-molecule hafnium chloride precursors facilitates precursor decomposition and the design of coating composition and structure. However, the use of chlorides corrodes equipment, and the emitted exhaust gases cause environmental pollution and pose safety concerns. In contrast, using large-molecule hafnium-containing organic precursors during the preparation process does not corrode equipment, and the exhaust gases do not pollute the environment, offering higher safety. However, it is difficult to directly prepare hafnium carbide coatings using conventional CVD processes with hafnium-containing organic precursors. Therefore, developing a safe and efficient method for preparing hafnium carbide coating materials based on hafnium-containing organic precursors is of significant importance and value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a safe and efficient preparation method for preparing hafnium carbide coatings based on hafnium-containing organic precursors.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] A safe and efficient method for preparing hafnium carbide coatings, using laser chemical vapor deposition, includes the following steps:

[0008] Substrate cleaning: The substrate used for the reaction is placed in an ultrasonic cleaner for cleaning to clean the substrate.

[0009] The equipment is connected by connecting the outlet of the raw material tank to the nozzle through the gas pipe, and then connecting the nozzle to the inlet of the deposition chamber of the laser chemical vapor deposition device. The inlet of the raw material tank is used to introduce the carrier gas, and the middle of the gas pipe is provided with a reaction inlet for introducing the reaction gas. The raw material tank contains the precursor.

[0010] Place the substrate into the deposition chamber of the laser chemical vapor deposition apparatus and position the substrate within the laser coverage area of ​​the laser chemical vapor deposition apparatus.

[0011] The equipment is evacuated, and the entire set of equipment is evacuated to create a vacuum environment inside the entire set of equipment.

[0012] The raw material tank is heated by heating the raw material tank, gas pipe and nozzle, so that the precursor in the raw material tank sublimates into precursor gas;

[0013] Construct a reaction environment and simultaneously introduce carrier gas and reactant gas, so that the carrier gas carries the precursor gas and reactant gas into the deposition chamber until the pressure in the deposition chamber is at the deposition pressure, and then stabilize for 5 minutes.

[0014] The reaction is carried out by turning on the laser to irradiate the substrate, causing the substrate surface to heat up to the reaction temperature. Then, it reacts with the precursor gas and the reactant gas to start the deposition reaction, which takes 10 minutes.

[0015] After the post-processing and deposition reaction are completed, the laser is turned off, the supply of carrier gas and reaction gas is stopped, the equipment is evacuated, and then the substrate is allowed to cool to room temperature before being removed and coated with a hafnium carbide coating.

[0016] The substrate is a carbon / carbon composite substrate or a graphite substrate, the precursor is a hafnium-containing organic compound, the carrier gas is argon, the reaction gas is CH4 and the dilution gas is H2.

[0017] Preferably, the gas pipe is provided with two reaction gas inlets for introducing CH4 and dilution gas H2 respectively.

[0018] Specifically, in the step of constructing the reaction environment, the flow rate of the introduced argon gas is 50~200 sccm, the flow rate of the introduced CH4 is 50~200 sccm, and the flow rate of the introduced dilution gas H2 is 300~1000 sccm.

[0019] Preferably, the precursor is hafnium acetylacetonate (Hf(acac)4), hafnium ethanol (Hf[C2H5O]4), and hafnium n-butanol (Hf[C4H5O]4). 10 O]4) is a mixture of at least one of them.

[0020] Preferably, the purity of CH4 is at least 99 vol%, the purity of argon is at least 99 vol%, and the purity of the diluent gas H2 is at least 99 vol.

[0021] Specifically, in the raw material tank addition step, the raw material tank, the gas pipe and the nozzle are heated to a temperature of 200~400℃.

[0022] Specifically, in the step of constructing the reaction environment, the deposition pressure is 400~1500 Pa.

[0023] Specifically, in the reaction step, the wavelength of the light emitted by the laser is between 700 and 1200 nm.

[0024] Specifically, the reaction temperature is 1550~1700℃.

[0025] The present invention has the following beneficial effects: By using functional hafnium-containing organic materials as precursors, the preparation process is environmentally friendly and highly safe. Furthermore, by utilizing the high energy density of laser light to directly act on the substrate, the decomposition of the precursor is effectively controlled, thereby controlling the composition and structure of the coating. This achieves the goal of safely and efficiently preparing hafnium carbide coatings. The resulting hafnium carbide coatings exhibit extremely high stability, possessing superior resistance to thermal shock and ablation, and a high deposition rate. The required hafnium carbide coating can be obtained in a short deposition time. This method is convenient to use, time-saving, and effectively reduces resource consumption. Attached Figure Description

[0026] Figure 1 The image shown is the XRD pattern of the product of Example 1 of this invention.

[0027] Figure 2 The images shown are electron microscope images of the product of Example 2 of the present invention, magnified to 5 μm (Figure a) and 10 μm (Figure b).

[0028] Figure 3 The image shows the XRD pattern of the product of Comparative Example 1 of this invention.

[0029] Figure 4 The image shows the XRD pattern of the product of Comparative Example 2 of this invention.

[0030] Figure 5 The image shows the XRD pattern of the product of Comparative Example 3 of this invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the embodiments.

[0032] A safe and efficient method for preparing a hafnium carbide coating according to Embodiment 1 of the present invention employs laser chemical vapor deposition and includes the following steps:

[0033] Substrate cleaning: The substrate used for the reaction is placed in an ultrasonic cleaner to clean the substrate thoroughly. This ensures that the substrate surface is clean, thereby ensuring that the hafnium carbide coating generated in the end is uniformly coated on the surface of the substrate. In this embodiment, the substrate used is a carbon / carbon composite material.

[0034] The equipment is connected by connecting the outlet of the raw material tank to the nozzle through a gas pipe, and then connecting the nozzle to the inlet of the deposition chamber of the laser chemical vapor deposition device. The gas inlet of the raw material tank is used to introduce the carrier gas. The middle of the gas pipe is provided with a reaction gas inlet for introducing the reaction gas. Preferably, there are two reaction gas inlets. The reaction gas is CH4 and the dilution gas is H2. The two reaction gas inlets are used to introduce CH4 and the dilution gas H2, respectively. The raw material tank contains a precursor, which is a hafnium-containing organic compound. In this embodiment, Hf(acac)4 is used.

[0035] Place the substrate into the deposition chamber of the laser chemical vapor deposition apparatus and position the substrate within the laser coverage area of ​​the apparatus; preferably, the laser can completely cover the upper surface of the substrate to ensure that the entire upper surface of the substrate is at the reaction temperature during the reaction, thereby ensuring that the upper surface of the substrate is uniformly covered with the hafnium carbide coating.

[0036] The equipment is evacuated to create a vacuum environment with a pressure of at least 20 Pa. Under vacuum conditions, there is no gas inside the equipment, ensuring that no air or other gases can affect the reaction.

[0037] The raw material tank, gas pipe, and nozzle are heated to sublimate the precursor in the raw material tank into a precursor gas. Specifically, in this step, the raw material tank is heated to 220°C, the gas pipe to 300°C, and the nozzle to 400°C. At 220°C, the precursor in the raw material tank reaches its sublimation temperature and sublimates into a precursor gas. Subsequently, when the precursor gas passes through the gas pipe and nozzle and meets the reaction gas, the temperature of the gas pipe ensures that the precursor gas will not change due to the influx of other gases, thus affecting the subsequent reaction. Furthermore, the gas is sprayed into the deposition chamber at 400°C, ensuring that the gas temperature remains at the sublimation temperature of the precursor for a short period of time, thereby effectively controlling the state of the reaction raw materials.

[0038] A reaction environment is constructed by simultaneously introducing a carrier gas and a reactant gas, allowing the carrier gas to carry the precursor gas and reactant gas into the deposition chamber until the pressure within the deposition chamber reaches the deposition pressure of 600 Pa, which is then stabilized for 5 minutes. Preferably, the flow rate of the introduced argon gas is 100 sccm, and the purity of the argon gas is 99.999 vol; the flow rate of the introduced CH4 gas is 100 sccm, and the purity of the CH4 gas is 99.999 vol; the flow rate of the introduced dilution gas H2 gas is 500 sccm, and the purity of the dilution gas H2 gas is 99.999 vol.

[0039] The reaction is carried out by turning on the laser to irradiate the substrate. In this embodiment, the wavelength of the laser emitted is 1000nm, which causes the substrate surface to start to heat up to the reaction temperature of 1550°C. Then, it reacts with the precursor gas and the reactant gas to start the deposition reaction, which takes 10 minutes.

[0040] In the post-processing stage, after the deposition reaction is completed, the laser is turned off, the supply of carrier gas and reaction gas is stopped, and the equipment is evacuated to remove the reaction environment, thereby reducing the generation of subsequent reactions. Then, the substrate is allowed to cool to room temperature, and the substrate is removed and coated with a hafnium carbide coating.

[0041] The XRD pattern of the hafnium carbide coating prepared in this embodiment is as follows: Figure 1 As shown, strong diffraction peaks of HfC and low-intensity diffraction peaks of hafnium oxide are observed, indicating a small amount of impurities. The test results demonstrate that a high-purity HfC coating was successfully prepared in this embodiment, and its sharp diffraction peaks indicate that HfC has high crystallinity.

[0042] A safe and efficient method for preparing a hafnium carbide coating according to Embodiment 2 of the present invention employs laser chemical vapor deposition and includes the following steps:

[0043] Substrate cleaning: The substrate used for the reaction is placed in an ultrasonic cleaner to clean the substrate thoroughly. This ensures that the substrate surface is clean, thereby ensuring that the hafnium carbide coating generated in the end is uniformly coated on the surface of the substrate. In this embodiment, a graphite substrate is used.

[0044] The equipment is connected by connecting the outlet of the raw material tank to a nozzle via a gas pipe, and then connecting the nozzle to the inlet of the deposition chamber of the laser chemical vapor deposition apparatus. The gas inlet of the raw material tank is used to introduce the carrier gas. The gas pipe has a reaction gas inlet in the middle for introducing the reaction gas. Preferably, there are two reaction gas inlets, and the reaction gas is CH4 and the dilution gas is H2. The two reaction gas inlets are used to introduce CH4 and the dilution gas H2, respectively. The raw material tank contains a precursor, which is a hafnium-containing organic compound. In this embodiment, the precursors used are Hf[C2H5O]4 and Hf[C4H10 O]4 is mixed in a 1:1 ratio.

[0045] Place the substrate into the deposition chamber of the laser chemical vapor deposition apparatus and position the substrate within the laser coverage area of ​​the apparatus; preferably, the laser can completely cover the upper surface of the substrate to ensure that the entire upper surface of the substrate is at the reaction temperature during the reaction, thereby ensuring that the upper surface of the substrate is uniformly covered with the hafnium carbide coating.

[0046] The equipment is evacuated to create a vacuum environment with a pressure of at least 20 Pa. Under vacuum conditions, there is no gas inside the equipment, ensuring that no air or other gases can affect the reaction.

[0047] The raw material tank, gas pipe, and nozzle are heated to sublimate the precursor in the raw material tank into a precursor gas. Specifically, in this step, the raw material tank is heated to 220°C, the gas pipe to 300°C, and the nozzle to 400°C. At 220°C, the precursor in the raw material tank reaches its sublimation temperature and sublimates into a precursor gas. Subsequently, when the precursor gas passes through the gas pipe and nozzle and meets the reaction gas, the temperature of the gas pipe ensures that the precursor gas will not change due to the influx of other gases, thus affecting the subsequent reaction. Furthermore, the gas is sprayed into the deposition chamber at 400°C, ensuring that the gas temperature remains at the sublimation temperature of the precursor for a short period of time, thereby effectively controlling the state of the reaction raw materials.

[0048] A reaction environment is constructed by simultaneously introducing a carrier gas and a reactant gas, allowing the carrier gas to carry the precursor gas and reactant gas into the deposition chamber until the pressure within the deposition chamber reaches the deposition pressure, which is 1000 Pa. The pressure is then stabilized for 5 minutes. Preferably, the flow rate of the introduced argon gas is 150 sccm, and the purity of the argon gas is 99.999 vol; the flow rate of the introduced CH4 gas is 150 sccm, and the purity of the CH4 gas is 99.999 vol; the flow rate of the introduced dilution gas H2 gas is 1000 sccm, and the purity of the dilution gas H2 gas is 99.999 vol.

[0049] The reaction is carried out by turning on the laser to irradiate the substrate. The wavelength of the laser light emitted is 1200nm, which causes the substrate surface to heat up to the reaction temperature of 1700℃. Then, it reacts with the precursor gas and the reactant gas to start the deposition reaction, which takes 10 minutes.

[0050] In the post-processing stage, after the deposition reaction is completed, the laser is turned off, the supply of carrier gas and reaction gas is stopped, and the equipment is evacuated to remove the reaction environment, thereby reducing the generation of subsequent reactions. Then, the substrate is allowed to cool to room temperature, and the substrate is removed and coated with a hafnium carbide coating.

[0051] The field emission scanning microscope image of the hafnium carbide coating prepared in this embodiment is shown below. Figure 2 As shown, the coating prepared in this embodiment is a dense coating composed of fine hafnium carbide particles, with a thickness of approximately 12 μm and a deposition rate of approximately 72 μm / h. Traditional CVD methods often use hafnium chloride as a precursor to prepare hafnium carbide coatings with deposition rates ranging from several to tens of micrometers per hour. In this method, the activation energy between raw material molecules is significantly reduced under laser activation, resulting in an extremely fast deposition rate, several to tens of times faster than traditional CVD methods.

[0052] This application discloses a method for preparing a hafnium carbide coating in Comparative Example 1. The materials used are the same as in Example 1, but a traditional CVD method is employed, with a temperature of 1100°C in the tube furnace. The resulting substrate is then subjected to XRD analysis to obtain the following results: Figure 3 The spectrum shows diffraction peaks for HfO2 and C, indicating that HfC diffraction peaks are not present on the carbon / carbon composite substrate. This suggests that no HfC is formed under these deposition conditions. In other words, hafnium carbide coatings cannot be prepared using hafnium-containing organics as precursors in conventional CVD.

[0053] The method for preparing a hafnium carbide coating in Comparative Example 2 of this application is basically the same as that in Example 1, except that the deposition temperature is 1400~1500℃. XRD analysis was performed on the obtained substrate to obtain the following results: Figure 4 The spectrum shows diffraction peaks for HfO2 and C, indicating that HfC was not formed under these deposition conditions. This is a carbon / carbon composite substrate.

[0054] The method for preparing a hafnium carbide coating in Comparative Example 3 of this application is basically the same as that in Example 2, except that the deposition pressure is 200 Pa. XRD analysis was performed on the obtained substrate to obtain the following results: Figure 5 The spectrum shows a strong diffraction peak for substrate C. This is because the pressure is low, the precursor content is low, and the excessive decomposition by the laser results in a thinner deposited coating. At the same time, diffraction peaks for HfC and HfO2 are also present, indicating the formation of a composite coating of HfC and HfO2 under these deposition conditions. However, the HfC content is low and cannot completely cover the substrate, thus exposing more of the substrate and failing to achieve the ablation resistance effect.

[0055] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A safe and efficient method for the preparation of hafnium carbide coating, characterized by, The laser chemical vapor deposition method comprises the following steps: Substrate cleaning, placing the substrate used for the reaction into an ultrasonic cleaning instrument for cleaning, and cleaning the substrate; Connecting equipment, connecting the gas outlet of the raw material tank to the nozzle through a gas pipe, and then connecting the nozzle to the inlet of the deposition cavity of the laser chemical vapor deposition device, wherein the gas inlet of the raw material tank is used for introducing carrier gas, the middle part of the gas pipe is provided with a reaction gas inlet for introducing reaction gas, and the raw material tank stores precursors; Placing the substrate, placing the substrate into the deposition cavity of the laser chemical vapor deposition device and making the substrate located in the laser coverage range of the laser chemical vapor deposition device; Vacuumizing the equipment, vacuumizing the entire equipment to make the interior of the entire equipment in a vacuum environment; Heating the raw material tank, heating the raw material tank, the gas pipe and the nozzle to make the precursors in the raw material tank sublimate into precursor gas; Constructing a reaction environment, introducing carrier gas and reaction gas at the same time to make the carrier gas drive the precursor gas and the reaction gas to enter the deposition cavity together until the pressure in the deposition cavity is in the deposition pressure, and then stabilizing for 5 minutes; Performing the reaction, opening the laser to irradiate the substrate to make the surface of the substrate start to warm up to the reaction temperature, then reacting with the precursor gas and the reaction gas to start the deposition reaction, and depositing for 10 minutes; Post-processing, after the deposition reaction is completed, the laser is turned off, the introduction of the carrier gas and the reaction gas is stopped, the equipment is vacuumized, then the substrate is cooled to room temperature, and the substrate is taken out, wherein the surface of the substrate is covered with a hafnium carbide coating; The substrate is a carbon / carbon composite material substrate or a graphite substrate, the precursor is a mixture of at least one of lanthanum acetylacetone, lanthanum ethanol and lanthanum n-butanol, the carrier gas is argon, and the reaction gas is CH4 and dilution gas H2.

2. The method of claim 1, wherein the method is characterized by: Two reaction gas inlets are arranged on the gas pipe for introducing the CH4 and the dilution gas H2, respectively.

3. The method of claim 2, wherein the method is characterized by: In the step of constructing the reaction environment, the flow rate of the introduced argon is 50-200 sccm, the flow rate of the introduced CH4 is 50-200 sccm, and the flow rate of the introduced dilution gas H2 is 300-1000 sccm.

4. The method of claim 1, wherein the method is characterized by: The purity of the CH4 is at least 99%, the purity of the argon is at least 99%, and the purity of the dilution gas H2 is at least 99%.

5. The method of claim 1, wherein the method is safe and efficient for producing the hafnium carbide coating. In the step of adding the raw material tank, the raw material tank, the gas pipe and the nozzle are heated to a temperature of 200-400 DEG C.

6. The method of claim 1, wherein the method is characterized by: In the step of constructing the reaction environment, the deposition pressure is 400-1500 Pa.

7. The method of claim 1, wherein the method is safe and efficient for producing the hafnium carbide coating. In the step of performing the reaction, the wavelength of the light emitted by the laser is 700-1200 nm.

8. The method of claim 7, wherein the method is characterized by: The reaction temperature is 1550-1700 DEG C.

Images