A method for ultrafast sintering of spherical aluminum nitride powder

Abstract

The application discloses a kind of spherical aluminium nitride powder ultrafast sintering preparation method, the method is, modified aluminium nitride powder, sintering auxiliary powder is proportioned and mixed according to mass ratio 1:20-30, after mixing evenly, wet ball milling is carried out, after wet ball milling, spray granulation is arranged glue, spherical granulation powder is obtained, then spherical granulation powder is sent into high-temperature rapid continuous sintering furnace and is rapidly sintered, the holding time of rapid sintering is 10-120s, and spherical aluminium nitride powder is obtained.The application uses surface passivation waterproof AlN powder as raw material instead of unconventional AlN powder, which can avoid the hydration of AlN powder into Al (OH) 3 during wet ball milling, resulting in the decrease of the thermal conductivity of sintered products;Rare earth nitrate is used as sintering aid, which helps to form uniform nanometer particle coating on the surface of AlN powder during spray granulation, and promotes liquid phase sintering.

Description

Technical Field

[0001] This invention relates to the field of nitride ceramics technology, and in particular to an ultrafast sintering preparation method for spherical aluminum nitride powder. Background Technology

[0002] Due to the inherent efficiency limitations of electronic devices, nearly 80% of the input electrical power is converted into waste heat. If the problems of waste heat dissipation and temperature control generated by electronic devices cannot be effectively solved, the temperature of electronic devices will rise, leading to a significant deterioration in the device's performance, reliability, and lifespan. High thermal conductivity polymer composite materials for electronic packaging and thermal interfaces are one of the key materials for solving the problem of waste heat dissipation in electronic devices.

[0003] Polymers, due to their inherently low thermal conductivity, typically require ceramic powder filling to improve their thermal conductivity. Spherical ceramic powders with high thermal conductivity are ideal fillers for preparing polymer composites with high processability, high filling capacity, and high thermal conductivity. Among various spherical ceramic fillers, spherical aluminum nitride powder possesses excellent thermal conductivity and electrical insulation properties, making it one of the important high thermal conductivity fillers. Developing new technologies for preparing spherical aluminum nitride powder is crucial for its application in electronic packaging and thermal interface materials.

[0004] Unlike spherical oxide powders, aluminum nitride is prone to hygroscopic hydration and decomposition and oxidation at high temperatures, making it difficult to prepare using conventional high-temperature melt spheroidization processes. Currently, spherical aluminum nitride thermally conductive fillers are mainly prepared by high-temperature sintering of spray-granulated powder. However, existing high-temperature sintering methods are limited by conventional processes, resulting in slow heating rates (≤20℃ / min) and long holding times (≥4h), leading to high energy consumption and high production costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a reasonable ultrafast sintering preparation method for preparing spherical aluminum nitride powder at low cost, based on a new ultrafast high-temperature sintering technology, which addresses the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing spherical aluminum nitride powder by ultrafast sintering is characterized by the following steps: Modified aluminum nitride powder and sintering aid powder are mixed in a mass ratio of 1:20-30. The modified aluminum nitride powder is a surface-passivated and waterproof AlN powder, and the sintering aid is a rare earth nitrate. After uniform mixing, the mixture is wet-milled, followed by spray granulation and debinding to obtain spherical granulated powder. The spherical granulated powder is then fed into a high-temperature rapid continuous sintering furnace for rapid sintering. The holding time for rapid sintering is 10-120 seconds, resulting in spherical aluminum nitride powder.

[0008] The technical problem to be solved by the present invention can also be achieved through the following technical solution: In the rapid sintering stage, the high-temperature rapid continuous sintering furnace is first evacuated to 50 Pa, and then 0.1 MPa of high-purity nitrogen gas is introduced into the high-temperature rapid continuous sintering furnace and the pressure is maintained. The inner cavity of the high-temperature rapid continuous sintering furnace is divided into three sections: the front section and the rear section are cooling zones, and the middle section is a high-temperature zone. The temperature of the cooling zone is controlled at 30℃-50℃, and the temperature of the high-temperature zone is controlled at 1700℃-1900℃. The spherical granulated powder after debinding is sent to the high-temperature zone and held for 50s-70s at a heating rate of 10℃ / s-1000℃ / s, and then sent out from the rear cooling zone.

[0009] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the modified aluminum nitride powder is a surface passivated and waterproof AlN powder, and its average particle size is 0.2μm-2.0μm.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solution, wherein the sintering aid powder is one or more of Y(NO3)3, La(NO3)3, Gd(NO3)3 and Yb(NO3)3.

[0011] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the temperature range of the high-temperature rapid continuous sintering furnace is 1800℃; the heating rate of the rapid sintering is 500℃ / s.

[0012] The technical problem to be solved by the present invention can also be achieved through the following technical solution: the particle size range of the spherical aluminum nitride powder is 10μm-200μm, and the tap density ranges from 2.0 to 2.1g / cm³. 3 .

[0013] Compared with the prior art, the ultrafast sintering preparation method of the present invention uses surface passivated and waterproof AlN powder instead of conventional AlN powder as raw material, which can avoid the transformation of AlN powder into Al(OH)3 during wet ball milling, which leads to a decrease in the thermal conductivity of granulated sintered products; using rare earth nitrates as sintering aids helps to form nanoparticles uniformly coated on the surface of AlN powder during spray granulation, promoting liquid phase sintering;

[0014] By using Joule radiation heating in a high-temperature rapid continuous sintering furnace, the spherical AlN granulated powder is rapidly heated, forming a supersaturated liquid phase that greatly accelerates its densification. At the same time, the dynamic feeding and discharging process is used to suppress liquid phase adhesion between spherical particles during sintering, thereby improving the dispersibility and filling properties of the spherical AlN powder.

[0015] The spherical aluminum nitride powder of the present invention can be used as a high thermal conductivity filler for electronic packaging and thermal interface materials, and its rapid sintering preparation method has the advantages of simple process, short preparation cycle and low cost. Attached Figure Description

[0016] Figure 1 The XRD pattern of the spherical aluminum nitride powder in Example 1 is shown below.

[0017] Figure 2 This is a SEM image of the spherical aluminum nitride powder from Example 2. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] A method for preparing spherical aluminum nitride powder by ultrafast sintering: Modified aluminum nitride powder and sintering aid powder are mixed in a mass ratio of 1:20-30. After uniform mixing, the mixture is wet ball-milled, spray-granulated and debinded to obtain spherical granulated powder. The spherical granulated powder is then fed into a high-temperature rapid continuous sintering furnace for rapid sintering. The holding time for rapid sintering is 10-120 seconds to obtain spherical aluminum nitride powder.

[0020] The modified aluminum nitride powder is a surface passivated and waterproof AlN powder with an average particle size of 0.2μm-2.0μm. The surface passivated and waterproof AlN powder can be obtained by conventional waterproofing treatment methods such as high-temperature pre-oxidation treatment and inorganic acid surface passivation.

[0021] The sintering aid powder is one or more of Y(NO3)3, La(NO3)3, Gd(NO3)3 and Yb(NO3)3;

[0022] The temperature range of the high-temperature rapid continuous sintering furnace is 1700℃-1900℃; the heating rate of the rapid sintering is 10℃ / s-1000℃ / s.

[0023] The spherical aluminum nitride powder has a particle size range of 10 μm-200 μm and a tap density range of 2.0-2.1 g / cm³. 3 .

[0024] Example 1

[0025] Modified AlN powder and Y(NO3)3 powder with an average particle size of 1.0μm were mixed at a mass ratio of AlN:Y(NO3)3 = 22:1. After adding dispersants and binders, the mixture was wet-milled and spray-granulated. After debinding, the powder was fed into a high-temperature rapid continuous sintering furnace at 1800℃. The furnace was evacuated to 50Pa by a pressure control system and then high-purity nitrogen gas at 0.1MPa was introduced and maintained at pressure. The water-cooling control system was turned on to maintain the furnace shell temperature at 40℃. The temperature control system parameters were set to raise the Joule heating element to 1800℃. After the temperature was stabilized, the feeding system controlled the feeding rate of the feeding hopper and the screw feeder. The debinded granulated powder was fed into the 1800℃ high-temperature zone of the furnace at a heating rate of 100℃ / s after passing through the front heat insulation sleeve and held for 90s. After being cooled by the rear heat insulation sleeve, the powder was sent to the discharge hopper to obtain spherical aluminum nitride powder.

[0026] The particle size range of the spherical aluminum nitride powder was measured to be 10 μm-200 μm, and the tap density was 2.05 g / cm³. XRD analysis was performed on the powder, and the results are as follows: Figure 1 As shown, the phase composition of the sample is mainly AlN, with a small amount of Y4Al2O9 formed by introducing sintering aids. SEM observation revealed that the prepared aluminum nitride powder has a spherical morphology. Epoxy resin-based composite materials were prepared by filling spherical aluminum nitride powder at a volume fraction of 50%, and the thermal conductivity of the composite material was measured to be 3.3 W / (m·K).

[0027] Example 2

[0028] Modified AlN powder and Gd(NO3)3 powder with an average particle size of 0.5 μm were mixed at a mass ratio of AlN:Gd(NO3)3 = 25:1. After adding dispersants and binders, the mixture was wet-milled and spray-granulated. After debinding, the granulated powder was fed into a high-temperature rapid continuous sintering furnace at 1850℃. The debinded spherical granules were then fed into the feed hopper of the furnace. The furnace was evacuated to 50 Pa using a pressure control system, and then high-purity gas was introduced at 0.1 MPa. Nitrogen gas is supplied and pressurized. The water-cooling control system is activated to maintain the furnace shell temperature at 30°C. The temperature control system parameters are set to raise the Joule heating element to 1850°C. Once the temperature is constant, the feeding system controls the feeding rate of the feeding hopper and the screw feeder. The granulated powder after glue removal is fed into the furnace body at a high temperature of 1850°C for 60 seconds through the front heat insulation sleeve and a heating rate of 500°C / s. After cooling through the rear heat insulation sleeve, it is sent to the discharge hopper to obtain spherical aluminum nitride powder.

[0029] The particle size range of the spherical aluminum nitride powder was measured to be 10 μm to 200 μm, and the tap density was 2.10 g / cm³. XRD analysis revealed that the phase composition of the sample was mainly AlN, with a small amount of GdAlO3 formed by introducing sintering aids. SEM observation showed that the prepared aluminum nitride powder had a spherical morphology, as shown in the results below. Figure 2 As shown, epoxy resin-based composite materials were prepared by filling spherical aluminum nitride powder with a volume fraction of 50%, and the thermal conductivity of the composite material was measured to be 3.4 W / (m·K).

[0030] Example 3

[0031] Modified AlN powder and La(NO3)3 powder with an average particle size of 0.2μm were mixed in a mass ratio of AlN:La(NO3)3 = 20:1. After adding dispersants and binders, the mixture was wet-milled and spray-granulated. After debinding, the powder was fed into a high-temperature rapid continuous sintering furnace at 1700℃. The furnace was evacuated to 50Pa by a pressure control system and then high-purity nitrogen gas at 0.1MPa was introduced and maintained at pressure. The water-cooling control system was turned on to maintain the furnace shell temperature at 40℃. The temperature control system parameters were set to raise the Joule heating element to 1700℃. After the temperature was stabilized, the feeding system controlled the feeding rate of the feeding hopper and the screw feeder. The debinded granulated powder was fed into the 1700℃ high-temperature zone of the furnace at a heating rate of 1000℃ / s after passing through the front heat insulation sleeve and held for 120s. After being cooled by the rear heat insulation sleeve, the powder was sent to the discharge hopper to obtain spherical aluminum nitride powder.

[0032] The particle size range of the spherical aluminum nitride powder was measured to be 10 μm to 200 μm, and the tap density was 2.00 g / cm³. XRD analysis revealed that the phase composition of the sample was mainly AlN, with a small amount of LaAlO₃ formed by introducing sintering aids. SEM observation confirmed that the prepared aluminum nitride powder had a spherical morphology. Epoxy resin-based composite materials were prepared by filling the spherical aluminum nitride powder with a 50% volume fraction. The thermal conductivity of the composite material was measured to be 3.1 W / (m·K).

[0033] Example 4

[0034] Modified AlN powder, Y(NO3)3 powder, and Yb(NO3)3 powder with an average particle size of 2.0 μm were mixed in a mass ratio of AlN:Y(NO3)3:Yb(NO3)3 = 60:1:1. After adding dispersants and binders, the mixture was wet-milled, spray-granulated, and after debinding, fed into a high-temperature rapid continuous sintering furnace at 1900℃. The furnace was then evacuated to 50 Pa using a pressure monitoring and control system, and high-purity nitrogen gas at 0.1 MPa was introduced and the pressure was maintained. The water-cooling control system is activated to ensure that the furnace shell temperature is below 50°C. The temperature control system parameters are set to raise the Joule heating element to 1900°C. After the temperature is constant, the feeding system controls the feeding rate of the feeding hopper and the screw feeder. The granulated powder after glue removal is fed into the furnace body at a high temperature zone of 1900°C for 10 seconds after passing through the front heat insulation sleeve. Then, after being cooled by the rear heat insulation sleeve, it is sent into the discharge hopper to obtain spherical aluminum nitride powder.

[0035] The particle size range of the spherical aluminum nitride powder was measured to be 10 μm to 200 μm, with a tap density of 2.10 g / cm³. XRD analysis revealed that the main phase composition of the sample was AlN. SEM observation confirmed that the prepared aluminum nitride powder had a spherical morphology. Epoxy resin-based composite materials were prepared by filling the spherical aluminum nitride powder with a 50% volume fraction. The thermal conductivity of the composite material was measured to be 3.2 W / (m·K).

[0036] Example 5

[0037] Modified AlN powder, Y(NO3)3 powder, Gd(NO3)3 powder, and La(NO3)3 powder with an average particle size of 1.5 μm were mixed in a mass ratio of AlN:Y(NO3)3:Gd(NO3)3:La(NO3)3 = 90:2:1:1. After adding dispersants and binders, the mixture was wet-milled, spray-granulated, and after debinding, fed into a high-temperature rapid continuous sintering furnace at 1750℃. The furnace was then evacuated to 50 Pa using a pressure control system, and 0.1 kJ / L gas was introduced. High-purity nitrogen at MPa is supplied and maintained at pressure. The water-cooling control system is activated to ensure the furnace shell temperature is 35℃. The temperature control system parameters are set to raise the Joule heating element to 1750℃. After the temperature is constant, the feeding system controls the feeding rate of the feeding hopper and the screw feeder. The granulated powder after glue removal is fed into the furnace body at a high temperature zone of 1750℃ for 90s after passing through the front heat insulation sleeve and heating rate of 800℃ / s. Then, after being cooled by the rear heat insulation sleeve, it is sent into the discharge hopper to obtain spherical aluminum nitride powder.

[0038] The particle size range of the spherical aluminum nitride powder was measured to be 10 μm to 200 μm, with a tap density of 2.10 g / cm³. XRD analysis revealed that the main phase composition of the sample was AlN. SEM observation confirmed that the prepared aluminum nitride powder had a spherical morphology. Epoxy resin-based composite materials were prepared by filling the spherical aluminum nitride powder with a 50% volume fraction. The thermal conductivity of the composite material was measured to be 3.3 W / (m·K).

[0039] Some embodiments

[0040] To examine the effects of sintering temperature, heating rate, and holding time on the tap density of spherical aluminum nitride powder, the same method and steps as in Example 1 were used, except that the heating rate and holding time were changed. The results are shown in the table below.

[0041]

[0042]

[0043] The results show that when the sintering temperature is below 1700℃, or the heating rate is below 10℃ / s, or the holding time is less than 10s, it is difficult to achieve sintering densification of granulated powder; when the sintering temperature is above 1900℃, or the heating rate is above 1000℃ / s, or the holding time is greater than 120s, the density of sintered spherical aluminum nitride powder will not be further improved.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for ultrafast sintering of spherical aluminum nitride powder, characterized in that, The method is that the modified aluminum nitride powder and the sintering aid powder are mixed in a mass ratio of 1:20-30, wherein the modified aluminum nitride powder is a surface passivated and waterproofed AlN powder, and the sintering aid is a rare earth nitrate; the mixture is uniformly wet ball milled, and then is spray granulated to remove glue, to obtain spherical granulated powder; the spherical granulated powder is sent into a high-temperature rapid continuous sintering furnace for rapid sintering, to obtain spherical aluminum nitride powder; In the rapid sintering stage, the high-temperature rapid continuous sintering furnace is first vacuumized to 50 Pa, then 0.1 MPa high-purity nitrogen is introduced into the high-temperature rapid continuous sintering furnace and is kept at a constant pressure; the inner cavity of the high-temperature rapid continuous sintering furnace is divided into three sections, the front section and the rear section are cooling zones, and the middle section is a high-temperature zone; the temperature of the cooling zones is controlled at 30-50°C, and the temperature of the high-temperature zone is controlled at 1700-1900°C; the spherical granulated powder after glue removal is sent to the high-temperature zone at a temperature rising rate of 10-1000°C / s and is kept for 50-70 s, and then is sent out from the rear cooling zone.

2. The method according to claim 1, wherein the method is characterized by: The high-temperature zone is heated by Joule radiation.

3. The method according to claim 1, wherein the method is characterized by: The average particle size of the modified aluminum nitride powder is 0.2-2.0 μm.

4. The method according to claim 1, wherein the method is characterized by: The sintering aid powder is one or more of Y(NO3)3, La(NO3)3, Gd(NO3)3 and Yb(NO3)3.

5. The method according to claim 1, wherein the method is characterized by: The temperature range of the high-temperature rapid continuous sintering furnace is 1800°C, and the temperature rising rate of the rapid sintering is 500°C / s.

6. The method according to claim 1, wherein the method is characterized by: The particle size of the spherical aluminum nitride powder ranges from 10 μm to 200 μm, and the tap density ranges from 2.0 to 2.1 g / cm 3 .

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