CN115772039A - Preparation method of silicon nitride heating body with heating film - Google Patents
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Abstract
The invention provides a preparation method of a silicon nitride heating element with a heating film, which comprises the following steps: s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling; s2, drying the powder subjected to ball milling, adding an auxiliary agent, and grinding; s3, single-side pressure molding is carried out on the ground powder; s4, placing the formed blank in a high-temperature furnace, and introducing nitrogen into the high-temperature furnace for reaction; s5, sintering the processed blank at a high temperature to obtain a heating body; s6, cleaning the heating body; s7, preparing a solution, spraying the solution on the surface of the cleaned heating element, and depositing to obtain a product. The invention ensures the close combination between the heating body and the heating film, improves the integral strength and the integral heat conversion rate.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a preparation method of a silicon nitride heating element with a heating film.
Background
The ceramic is used as a heating body substrate, the insulating property is good, the ceramic is more and more widely applied to heating products, particularly, a silicon nitride ceramic material with excellent comprehensive performance is provided, the theoretical thermal conductivity of single crystal silicon nitride is high, the ultra-high power density can be borne, and the prepared heating body has excellent heat transmission and heat cycle resistance. Meanwhile, the tin dioxide film has excellent physicochemical characteristics such as high hardness, high light transmittance, high conductivity, high temperature resistance, thermal stability and the like. However, when both are combined, the heat conversion rate of the heat generating body needs to be further improved.
Therefore, the development of a preparation method of a silicon nitride heating element with a heating film not only has urgent research value, but also has good economic benefit and industrial application potential, which is the basis and the place where the invention can be completed.
Disclosure of Invention
The invention aims to provide a preparation method of a silicon nitride heating element with a heating film, which effectively combines a tin dioxide film and the silicon nitride heating element and improves the overall heat conversion rate.
The invention provides a preparation method of a silicon nitride heating element with a heating film, which comprises the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling;
s2, drying the powder subjected to ball milling, adding an auxiliary agent, and grinding;
s3, single-side pressure molding is carried out on the ground powder;
s4, placing the formed blank in a high-temperature furnace, and introducing nitrogen into the high-temperature furnace for reaction;
s5, sintering the processed blank at a high temperature to obtain a heating element;
s6, cleaning the heating body;
s7, preparing a solution, spraying the solution on the surface of the cleaned heating element, and depositing to obtain a product.
As a preferable technical solution, in the step S1, the weight ratio of the silicon powder, the aluminum powder and the silicon carbide powder is 9:3-7: and 4, adding the silicon powder, the aluminum powder and the silicon carbide powder in sequence of the silicon carbide powder, half of the weight of the silicon powder, the aluminum powder and the other half of the weight of the silicon powder.
As a preferable technical scheme, in the step S1, the ball milling speed is 300 to 500 rpm, wherein the ball milling time is 0.5 to 1 hour after adding silicon carbide powder and half of the weight of silicon powder, the ball milling time is continued for 20 minutes after adding aluminum powder, and the ball milling time is continued for 1 to 1.5 hours after adding the other half of the weight of silicon powder.
As a preferable technical solution, in step S1, during the ball milling process, ethanol is added, wherein the first ethanol addition is performed when half of the silicon carbide powder and half of the silicon powder by weight are added, the second ethanol addition is performed after the aluminum powder is added, and the third ethanol addition is performed when the other half of the silicon powder by weight are added.
As a preferable technical scheme, in the step S2, the drying is carried out at 85-95 ℃ for 25-30 hours.
As a preferable technical solution, in step S2, the auxiliary agent is microcrystalline cellulose and a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution with a concentration of 8.5wt%, and the weight ratio of microcrystalline cellulose to polyvinyl alcohol solution is 1:70-75.
As a preferable technical scheme, in the step S3, the forming pressure is 120-150MPa, and the pressure duration is 50-60 seconds.
As a preferred technical scheme, in the step S4, the blank body is firstly placed in a high-temperature furnace which is not opened, and is kept stand for 8 to 9 hours; then raising the temperature to 400 ℃ at the temperature raising speed of 5-15 ℃/h, and introducing a small amount of N 2 And vacuumized to obtainPumping for 1.5 hours, wherein the pumping is performed once every half hour, and the negative pressure in the furnace is basically kept; after the evacuation was completed, the formal aeration was started, and the volume ratio of nitrogen gas: introducing gas according to the proportion of hydrogen = 95; keeping the temperature rise rate of 5-15 ℃/h to 500 ℃, and keeping the temperature for 5 h; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then powering off, closing the gas inlet and outlet valve, and cooling by water cooling.
As a preferable technical solution, in step S5, the processed blanks are cleaned, then the surfaces are coated with paint, and silicon nitride powder is filled between the blanks.
As a preferable technical scheme, the coating adopts a mixture of sodium silicate, boron nitride and ethanol, and the weight ratio is 3:2:5.
as a preferable technical scheme, in step S6, the heating element is sequentially soaked in a hydrochloric acid solution, distilled water, a sodium hydroxide solution and distilled water, washed, then placed in absolute ethyl alcohol, washed for 10min with ultrasonic waves, taken out, then placed in an oven for drying, and finally placed in a plasma cleaning machine for washing for 30min.
As a preferable technical solution, in step S7, analytically pure SnCl is used for the solution 4 ·5H 2 O and SbCl 3 Preparing a solution from the raw material and absolute ethyl alcohol as a solvent, wherein the solution is SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (A) to (B) is 5:1.
as a preferable technical proposal, in the step S7, the heating element is firstly heated to 450 ℃, and the flow rate of the solution spraying is 0.5ml/cm 2 Spraying 30 times at intervals of 2min each time; and after the spraying is finished, the heating element is placed in an environment with the temperature of 500 ℃ for heat preservation for 10min and then cooled to the room temperature along with the furnace.
The invention has the following beneficial effects:
the invention provides a preparation method of a silicon nitride heating element with a heating film, which adopts a silicon nitride heating element prepared by a specific process, wherein the silicon carbide powder, aluminum powder and silicon powder are adopted as raw materials, the silicon powder is added in two batches in grinding and dispersing, and simultaneously, microcrystalline cellulose,The polyvinyl alcohol solution is used as an auxiliary agent, so that the mixing degree of the raw materials is greatly improved, and favorable conditions are provided for subsequent high-temperature nitridation treatment of the blank. The blank body adopts a high-temperature nitriding process, and the process steps are obtained by a large number of repeated tests of an inventor, wherein the adopted gradual heating process is carried out by the inventor on the basis of specific raw materials and additives, so that the nitriding effect is ensured, and meanwhile, the density of a heating body is more uniform and the thermal conductivity is more excellent; the density of the heating element is uniform, a foundation is provided for the preparation of a heating film in the next step, and SnCl is adopted in the preparation of the heating film 4 ·5H 2 O and SbCl 3 The raw materials are sprayed at intervals, so that the tight combination between the heating body and the heating film is ensured, the integral strength is improved, and the integral heat conversion rate is also improved.
Detailed Description
The invention is further illustrated by the following specific examples. However, the use and purpose of these exemplary embodiments are only to exemplify the present invention, and do not constitute any limitation in any form to the actual scope of the present invention, and do not limit the scope of the present invention.
Example 1
A preparation method of a silicon nitride heating element with a heating film comprises the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling, wherein the weight ratio of the silicon powder to the aluminum powder to the silicon carbide powder is 9:3:4, adding silicon carbide powder, aluminum powder and silicon carbide powder in the order of silicon carbide powder, half of the weight of silicon powder, aluminum powder and the other half of the weight of silicon powder, wherein the ball milling speed is 300 r/min, the ball milling time is 0.5 hour after adding the silicon carbide powder and the half of the weight of silicon powder, the ball milling time is continued for 20 minutes after adding the aluminum powder, the ball milling time is continued for 1 hour after adding the other half of the weight of silicon powder, and ethanol is added in the ball milling process, wherein the ethanol is added for the first time when the silicon carbide powder and the half of the weight of silicon powder are added, the ethanol is added for the second time after the aluminum powder is added, and the ethanol is added for the third time when the other half of the weight of silicon powder is added;
s2, drying the powder subjected to ball milling at 85 ℃ for 25 hours, adding an auxiliary agent, wherein the auxiliary agent is microcrystalline cellulose and a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution with the concentration of 8.5wt%, and the weight ratio of the microcrystalline cellulose to the polyvinyl alcohol solution is 1:70, grinding;
s3, single-side pressing and molding the ground powder, wherein the molding pressure is 120MPa, and the pressure duration is 50 seconds;
s4, placing the formed blank body in a high-temperature furnace, introducing nitrogen into the high-temperature furnace for reaction, specifically, placing the blank body in the unopened high-temperature furnace, standing for 8 hours to enable the blank body to adapt to the temperature in the furnace, so as to ensure that the whole blank body has a uniform temperature field and prevent the blank body from cracking due to thermal stress in the temperature rising process; then the temperature is raised to 400 ℃ at the temperature raising speed of 5 ℃/hour, and a small amount of N is introduced 2 Vacuumizing for 1.5 hours, wherein the vacuumizing is performed once every half hour, and the negative pressure in the furnace is basically kept; after the evacuation was completed, the formal aeration was started, and the volume ratio of nitrogen gas: introducing gas according to the proportion of hydrogen = 95; keeping the temperature rise rate of 5 ℃/hour to 500 ℃, and keeping the temperature for 5 hours; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then powering off, closing the gas inlet and outlet valve, and cooling by water cooling;
s5, cleaning the processed blanks, coating paint on the surfaces, filling silicon nitride powder between the blanks, and sintering at high temperature to obtain a heating body, wherein the paint is a mixture of sodium silicate, boron nitride and ethanol, and the weight ratio is 3:2:5,;
s6, sequentially putting the heating element into a hydrochloric acid solution, distilled water, a sodium hydroxide solution and distilled water for soaking, putting the heating element into absolute ethyl alcohol after cleaning, cleaning the heating element for 10min by using ultrasonic waves, taking the heating element out, putting the heating element into an oven for drying, finally putting the heating element into a plasma cleaning machine for cleaning for 30 min;
s7, preparing a solution by adopting analytically pure SnCl 4 ·5H 2 O and SbCl 3 Is composed of the raw materials are mixed and stirred to prepare the raw material,the solution is prepared by using absolute ethyl alcohol as a solvent, wherein the SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (A) to (B) is 5:1, heating the heating element to 450 ℃ at first, and spraying the solution at the flow rate of 0.5ml/cm 2 Spraying for 30 times by a spray pyrolysis film coating machine at an interval of 2min each time; and after the spraying is finished, the heating body is placed in an environment with the temperature of 500 ℃ for heat preservation for 10min, then the heating body is cooled to the room temperature along with the furnace, and a product is obtained after deposition.
Example 2
A preparation method of a silicon nitride heating element with a heating film comprises the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling, wherein the weight ratio of the silicon powder to the aluminum powder to the silicon carbide powder is (9): 7:4, adding silicon carbide powder, aluminum powder and silicon carbide powder in sequence, wherein the ball milling speed is 500 r/min, the ball milling time is 1 hour after the silicon carbide powder and half of the silicon powder are added, the ball milling time is continued for 20 minutes after the aluminum powder is added, the ball milling time is continued for 1.5 hours after the other half of the silicon powder is added, and ethanol is added in the ball milling process, wherein the ethanol is added for the first time when the silicon carbide powder and half of the silicon powder are added, the ethanol is added for the second time after the aluminum powder is added, and the ethanol is added for the third time when the other half of the silicon powder is added;
s2, drying the powder subjected to ball milling at 95 ℃ for 30 hours, adding an auxiliary agent, wherein the auxiliary agent is microcrystalline cellulose and a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution with the concentration of 8.5wt%, and the weight ratio of the microcrystalline cellulose to the polyvinyl alcohol solution is 1:75, grinding;
s3, pressurizing and molding the single surface of the ground powder, wherein the molding pressure is 150MPa, and the pressure duration is 60 seconds;
s4, placing the formed blank body in a high-temperature furnace, introducing nitrogen into the high-temperature furnace for reaction, specifically, placing the blank body in the unopened high-temperature furnace, standing for 9 hours to enable the blank body to adapt to the temperature in the furnace, so as to ensure that the whole blank body has a uniform temperature field and prevent the temperature rise process due to the fact that the temperature of the whole blank body is uniformCracking of the blank that occurs from thermal stress; then the temperature is raised to 400 ℃ at the temperature rise speed of 15 ℃/hour, and a small amount of N is introduced 2 Vacuumizing for 1.5 hours, wherein the vacuumizing is performed once every half hour, and the negative pressure in the furnace is basically kept; after the vacuum pumping is finished, formal ventilation is started, and the volume ratio of nitrogen: introducing gas according to the proportion of hydrogen =95 and 5, maintaining positive pressure in the furnace, keeping bubbling in the gas outlet cylinder continuously, and paying attention to not excessively violent use of nitrogen; keeping the temperature rise rate of 15 ℃/hour to 500 ℃, and keeping the temperature for 5 hours; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then powering off, closing the gas inlet and outlet valve, and cooling by water cooling;
s5, cleaning the processed blanks, coating paint on the surfaces, filling silicon nitride powder between the blanks, and sintering at high temperature to obtain a heating body, wherein the paint is a mixture of sodium silicate, boron nitride and ethanol, and the weight ratio is 3:2:5;
s6, sequentially putting the heating element into a hydrochloric acid solution, distilled water, a sodium hydroxide solution and distilled water for soaking, putting the heating element into absolute ethyl alcohol after cleaning, cleaning the heating element for 10min by using ultrasonic waves, taking the heating element out, putting the heating element into an oven for drying, finally putting the heating element into a plasma cleaning machine for cleaning for 30 min;
s7, preparing a solution by adopting analytically pure SnCl 4 ·5H 2 O and SbCl 3 Preparing a solution from the raw material and absolute ethyl alcohol as a solvent, wherein the solution is SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (A) to (B) is 5:1, heating the heating element to 450 ℃, wherein the flow rate of solution spraying is 0.5ml/cm 2 Spraying for 30 times by a spray pyrolysis film coating machine at the interval of 2min each time; and after the spraying is finished, the heating body is placed in an environment with the temperature of 500 ℃ for heat preservation for 10min, then the heating body is cooled to the room temperature along with the furnace, and a product is obtained after deposition.
Example 3
A preparation method of a silicon nitride heating element with a heating film comprises the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling, wherein the weight ratio of the silicon powder to the aluminum powder to the silicon carbide powder is (9): 5:4, adding silicon carbide powder, aluminum powder and silicon carbide powder in the order of silicon carbide powder, half of the weight of silicon powder, aluminum powder and the other half of the weight of silicon powder, wherein the ball milling speed is 400 r/min, the ball milling time is 0.8 h after adding the silicon carbide powder and the half of the weight of silicon powder, the ball milling time is continued for 20 min after adding the aluminum powder, the ball milling time is continued for 1.2 h after adding the other half of the weight of silicon powder, and in the ball milling process, ethanol is added, wherein the ethanol is added for the first time when the silicon carbide powder and the half of the weight of silicon powder are added, the ethanol is added for the second time after the aluminum powder is added, and the ethanol is added for the third time when the other half of the weight of silicon powder is added;
s2, drying the powder subjected to ball milling at 90 ℃ for 28 hours, adding an auxiliary agent, wherein the auxiliary agent is microcrystalline cellulose and a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution with the concentration of 8.5wt%, and the weight ratio of the microcrystalline cellulose to the polyvinyl alcohol solution is 1:72, grinding;
s3, pressurizing and molding the single surface of the ground powder, wherein the molding pressure is 135MPa, and the pressure duration is 55 seconds;
s4, placing the formed blank body in a high-temperature furnace, introducing nitrogen into the high-temperature furnace for reaction, specifically, placing the blank body in the unopened high-temperature furnace, standing for 8.5 hours to enable the blank body to adapt to the temperature in the furnace, so as to ensure that the whole blank body has a uniform temperature field and prevent the blank body from cracking due to thermal stress in the heating process; then the temperature is raised to 400 ℃ at the temperature raising speed of 10 ℃/hour, and a small amount of N is introduced 2 Vacuumizing for 1.5 hours, and vacuumizing once every half hour, wherein the negative pressure in the furnace is basically kept; after the evacuation was completed, the formal aeration was started, and the volume ratio of nitrogen gas: introducing gas according to the proportion of hydrogen = 95; keeping the heating rate of 10 ℃/hour to 500 ℃, and keeping the temperature for 5 hours; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then cutting off the power, closing the gas inlet and outlet valve, and cooling by water cooling;
s5, cleaning the processed blanks, coating paint on the surfaces, filling silicon nitride powder between the blanks, and sintering at high temperature to obtain a heating body, wherein the paint is a mixture of sodium silicate, boron nitride and ethanol, and the weight ratio is 3:2:5,;
s6, sequentially putting the heating element into a hydrochloric acid solution, distilled water, a sodium hydroxide solution and distilled water for soaking, putting the heating element into absolute ethyl alcohol after cleaning, cleaning the heating element for 10min by using ultrasonic waves, taking the heating element out, putting the heating element into an oven for drying, finally putting the heating element into a plasma cleaning machine for cleaning for 30 min;
s7, preparing a solution by adopting analytically pure SnCl 4 ·5H 2 O and SbCl 3 Preparing solution with anhydrous ethanol as solvent, wherein SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (A) to (B) is 5:1, heating the heating element to 450 ℃, wherein the flow rate of solution spraying is 0.5ml/cm 2 Spraying for 30 times by a spray pyrolysis film coating machine at an interval of 2min each time; and after the spraying is finished, the heating body is placed in an environment of 500 ℃ for heat preservation for 10min, then is cooled to room temperature along with the furnace, and a product is obtained after deposition.
Example 4
A preparation method of a silicon nitride heating element with a heating film comprises the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling, wherein the weight ratio of the silicon powder to the aluminum powder to the silicon carbide powder is 9:3:4, adding silicon carbide powder, aluminum powder and silicon carbide powder in the order of silicon carbide powder, half of the weight of silicon powder, aluminum powder and the other half of the weight of silicon powder, wherein the ball milling speed is 500 r/min, the ball milling time is 0.5 hour after adding the silicon carbide powder and the half of the weight of silicon powder, the ball milling time is continued for 20 minutes after adding the aluminum powder, the ball milling time is continued for 1.5 hours after adding the other half of the weight of silicon powder, and ethanol is added in the ball milling process, wherein the ethanol is added for the first time when the silicon carbide powder and the half of the weight of silicon powder are added, the ethanol is added for the second time after the aluminum powder is added, and the ethanol is added for the third time when the other half of the weight of silicon powder is added;
s2, drying the powder subjected to ball milling at 85 ℃ for 30 hours, adding an auxiliary agent, wherein the auxiliary agent is microcrystalline cellulose and a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution with the concentration of 8.5wt%, and the weight ratio of the microcrystalline cellulose to the polyvinyl alcohol solution is 1:70, grinding;
s3, pressurizing and molding the single surface of the ground powder, wherein the molding pressure is 150MPa, and the pressure duration is 50 seconds;
s4, placing the formed blank body in a high-temperature furnace, introducing nitrogen into the high-temperature furnace for reaction, specifically, placing the blank body in the unopened high-temperature furnace, standing for 9 hours to enable the blank body to adapt to the temperature in the furnace, so as to ensure that the whole blank body has a uniform temperature field and prevent the blank body from cracking due to thermal stress in the temperature rising process; then the temperature is raised to 400 ℃ at the temperature raising speed of 5 ℃/hour, and a small amount of N is introduced 2 Vacuumizing for 1.5 hours, and vacuumizing once every half hour, wherein the negative pressure in the furnace is basically kept; after the evacuation was completed, the formal aeration was started, and the volume ratio of nitrogen gas: introducing gas according to the proportion of hydrogen =95 and 5, maintaining positive pressure in the furnace, keeping bubbling in the gas outlet cylinder continuously, and paying attention to not excessively violent use of nitrogen; keeping the temperature rise rate of 15 ℃/hour to 500 ℃, and keeping the temperature for 5 hours; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then cutting off the power, closing the gas inlet and outlet valve, and cooling by water cooling;
s5, cleaning the processed blanks, coating paint on the surfaces, filling silicon nitride powder between the blanks, and sintering at high temperature to obtain a heating body, wherein the paint is a mixture of sodium silicate, boron nitride and ethanol, and the weight ratio is 3:2:5,;
s6, sequentially putting the heating element into a hydrochloric acid solution, distilled water, a sodium hydroxide solution and distilled water for soaking, putting the heating element into absolute ethyl alcohol after cleaning, cleaning the heating element for 10min by using ultrasonic waves, taking the heating element out, putting the heating element into an oven for drying, finally putting the heating element into a plasma cleaning machine for cleaning for 30 min;
s7, preparing a solution by adopting analytically pure SnCl 4 ·5H 2 O and SbCl 3 Preparing a solution from the raw material and absolute ethyl alcohol as a solvent, wherein the solution is SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (A) to (B) is 5:1, heating the heating element to 450 ℃, wherein the flow rate of solution spraying is 0.5ml/cm 2 Spraying 30 times at intervals of 2min each time; and after the spraying is finished, the heating body is placed in an environment with the temperature of 500 ℃ for heat preservation for 10min, then the heating body is cooled to the room temperature along with the furnace, and a product is obtained after deposition.
Example 5
A preparation method of a silicon nitride heating element with a heating film comprises the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling, wherein the weight ratio of the silicon powder to the aluminum powder to the silicon carbide powder is (9): 7:4, adding silicon carbide powder, aluminum powder and silicon carbide powder in sequence, wherein the ball milling speed is 300 r/min, the ball milling time is 1 hour after the silicon carbide powder and the silicon powder with the half weight are added, the ball milling time is continued for 20 minutes after the aluminum powder is added, the ball milling time is continued for 1 hour after the silicon powder with the other half weight is added, and ethanol is added in the ball milling process, wherein the ethanol is added for the first time when the silicon carbide powder and the silicon powder with the half weight are added, the ethanol is added for the second time after the aluminum powder is added, and the ethanol is added for the third time when the silicon powder with the other half weight is added;
s2, drying the powder subjected to ball milling at 90 ℃ for 29 hours, adding an auxiliary agent, wherein the auxiliary agent is microcrystalline cellulose and a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution with the concentration of 8.5wt%, and the weight ratio of the microcrystalline cellulose to the polyvinyl alcohol solution is 1:71, grinding;
s3, pressurizing and molding the single surface of the ground powder, wherein the molding pressure is 145MPa, and the pressure duration is 57 seconds;
s4, placing the formed blank body in a high-temperature furnace, introducing nitrogen into the high-temperature furnace for reaction, specifically, placing the blank body in the unopened high-temperature furnace, standing for 8.5 hours to enable the blank body to adapt to the temperature in the furnace, so as to ensure that the whole blank body has a uniform temperature field and prevent the blank body from cracking due to thermal stress in the temperature rising process; then the temperature is raised to 400 ℃ at the heating rate of 8 ℃/hour, and a small amount of N is introduced 2 And draw outVacuumizing for 1.5 hours, and vacuumizing once every half hour, wherein the negative pressure in the furnace is basically kept; after the evacuation was completed, the formal aeration was started, and the volume ratio of nitrogen gas: introducing gas according to the proportion of hydrogen = 95; keeping the heating rate of 13 ℃/hour to 500 ℃, and keeping the temperature for 5 hours; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then powering off, closing the gas inlet and outlet valve, and cooling by water cooling;
s5, cleaning the processed blanks, coating paint on the surfaces, filling silicon nitride powder between the blanks, and sintering at high temperature to obtain a heating body, wherein the paint is a mixture of sodium silicate, boron nitride and ethanol, and the weight ratio is 3:2:5,;
s6, sequentially putting the heating element into a hydrochloric acid solution, distilled water, a sodium hydroxide solution and distilled water for soaking, putting the heating element into absolute ethyl alcohol after cleaning, cleaning the heating element for 10min by using ultrasonic waves, taking the heating element out, putting the heating element into an oven for drying, and finally putting the heating element into a plasma cleaning machine for cleaning for 30 min;
s7, preparing a solution by adopting analytically pure SnCl 4 ·5H 2 O and SbCl 3 Preparing solution with anhydrous ethanol as solvent, wherein SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (A) to (B) is 5:1, heating the heating element to 450 ℃ at first, and spraying the solution at the flow rate of 0.5ml/cm 2 Spraying 30 times at intervals of 2min each time; and after the spraying is finished, the heating body is placed in an environment with the temperature of 500 ℃ for heat preservation for 10min, then the heating body is cooled to the room temperature along with the furnace, and a product is obtained after deposition.
Comparative example 1
The preparation of the silicon nitride heating element adopts a general forming method, namely, silicon powder is pressed into a green body with a required shape, and the green body is placed into a nitriding furnace to be subjected to pre-nitriding (partial nitriding) sintering treatment; and performing complete nitridation sintering on the green body again to obtain the silicon nitride heating element.
Steps S6 and S7 are the same as those of embodiment 3.
Comparative example 2
Essentially identical to the procedure of example 3, with the difference that: in step S2, the auxiliary agent is only polyvinyl alcohol solution.
Comparative example 3
Essentially identical to the procedure of example 3, with the difference that: in step S4, a high-temperature nitridation mode of directly heating to 600 ℃, introducing nitrogen and maintaining the temperature is adopted.
Comparative example 4
Essentially identical to the procedure of example 3, with the difference that: in step S7, the solution is coated by silk screen printing.
The products of examples 1-5 and comparative examples 1-4 were tested for thermal conversion performance:
the products prepared in examples 1 to 5 and comparative examples 1 to 4 were prepared into a heat-generating body of the same specification, and the heat-generating body was subjected to energization heating with a direct current of 13.5V,500mA at a temperature of 27 ℃ and a humidity of 80% RH, a temperature rise test was carried out under the same conditions, energization was first carried out to raise the surface temperature of the heat-generating body to the maximum and reach equilibrium, and the test was repeated 50 times, and the test results were recorded as follows:
| example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example 4 |
| 96.2％ | 95.7％ | 97.5％ | 93.5％ | 96.1％ | 79.3％ | 89.2％ | 87.4％ | 86.7％ |
It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should also be understood that various alterations, modifications and/or variations can be made to the present invention by those skilled in the art after reading the technical content of the present invention, and all such equivalents fall within the protective scope defined by the claims of the present application.
Claims (10)
1. A preparation method of a silicon nitride heating element with a heating film is characterized by comprising the following steps:
s1, adding and mixing silicon powder, aluminum powder and silicon carbide powder according to a specific sequence, and performing ball milling;
s2, drying the powder subjected to ball milling, adding an auxiliary agent, and grinding;
s3, single-side pressure molding is carried out on the ground powder;
s4, placing the formed blank body in a high-temperature furnace, and introducing nitrogen into the high-temperature furnace for reaction;
s5, sintering the processed blank at a high temperature to obtain a heating element;
s6, cleaning the heating element;
s7, preparing a solution, spraying the solution on the surface of the cleaned heating element, and depositing to obtain a product.
2. The method of manufacturing a silicon nitride heat-generating body having a heat-generating film according to claim 1, wherein in step S1, the weight ratio of the silicon powder, the aluminum powder, and the silicon carbide powder is 9:3-7: and 4, adding the silicon powder, the aluminum powder and the silicon carbide powder in sequence of the silicon carbide powder, half weight of the silicon powder, the aluminum powder and the other half weight of the silicon powder.
3. The method of claim 2, wherein in step S1, the ball milling rate is 300 to 500 rpm, wherein after adding silicon carbide powder and half of the weight of silicon powder, the ball milling time is 0.5 to 1 hour, after adding aluminum powder, the ball milling time is continued for 20 minutes, and after adding the other half of the weight of silicon powder, the ball milling time is continued for 1 to 1.5 hours.
4. A method for preparing a silicon nitride heat-generating body having a heat-generating film according to claim 3, wherein in the step S1, ethanol is added during the ball milling, wherein the first ethanol addition is performed when half the weight of the silicon powder and the silicon carbide powder are added, the second ethanol addition is performed after the aluminum powder is added, and the third ethanol addition is performed when the other half weight of the silicon powder is added.
5. A method of producing a silicon nitride heat-generating body having a heat-generating film according to claim 1, wherein in the step S2, at the time of drying, drying is carried out at 85 to 95 ℃ for 25 to 30 hours.
6. A method of manufacturing a silicon nitride heat-generating body having a heat-generating film according to claim 5, wherein in step S2, the auxiliary agent is microcrystalline cellulose or a polyvinyl alcohol solution, the polyvinyl alcohol solution is a solution having a concentration of 8.5wt%, and the weight ratio of microcrystalline cellulose to polyvinyl alcohol solution is 1:70-75.
7. A method for producing a silicon nitride heat-generating body having a heat-generating film as described in claim 1, wherein in the step S4, the green body is first placed in a high temperature furnace which is not opened and left standing for 8 to 9 hours; then raising the temperature to 400 ℃ at the temperature raising speed of 5-15 ℃/h, and introducing a small amount of N 2 Vacuumizing for 1.5 hours, wherein the vacuumizing is performed once every half hour, and the negative pressure in the furnace is basically kept; after the vacuum pumping is finished, formal ventilation is started, and the volume ratio of nitrogen: introducing gas according to the proportion of hydrogen = 95; keeping the temperature rise rate of 5-15 ℃/h to 500 ℃, and keeping the temperature for 5 h; keeping the volume ratio and the flow of the gas unchanged, continuously heating to 600 ℃, keeping the temperature for 20 hours, then powering off, closing the gas inlet and outlet valve, and cooling by water cooling.
8. A method of producing a silicon nitride heat-generating body having a heat-generating film according to claim 1, wherein in step S5, the processed green bodies are cleaned, then the surfaces are coated with a paint, and silicon nitride powder is filled between the green bodies.
9. A method for producing a silicon nitride heat-generating body having a heat-generating film as described in claim 8, wherein said paint is a mixture of sodium silicate, boron nitride, and ethanol in a weight ratio of 3:2:5.
10. a method of producing a silicon nitride heat-generating body having a heat-generating film as described in claim 1, wherein in the step S7, the solution is analytically pure SnCl 4 ·5H 2 O and SbCl 3 Preparing a solution from the raw material and absolute ethyl alcohol as a solvent, wherein the solution is SnCl 4 ·5H 2 O and SbCl 3 The weight ratio of (1) is 5:1; firstly, the heating element is heated to 450 ℃, and the flow rate of the solution spraying is 0.5ml/cm 2 Spraying 30 times at intervals of 2min each time; and after the spraying is finished, the heating body is placed in an environment of 500 ℃ for heat preservation for 10min and then cooled to room temperature along with the furnace.
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