Preparation method of aluminum nitride-yttrium oxide composite powder and application thereof

Abstract

The application relates to the field of inorganic powder preparation, and particularly discloses a preparation method of aluminum nitride-yttrium oxide composite powder and application thereof. The preparation method of the aluminum nitride-yttrium oxide composite powder comprises the following steps: (1) dispersing an aluminum source, a yttrium source, a carbon source and a precipitating agent in water as a dispersion medium, and then performing a hydrothermal reaction to obtain a precursor; the carbon source is an organic substance capable of being hydrothermally carbonized; the precipitating agent can generate hydroxyl ions; (2) calcining the precursor in a nitrogen-containing atmosphere to obtain a nitridation product; the calcination temperature is 1300-1600 DEG C; and (3) performing carbon removal treatment on the nitridation product in an oxygen-containing atmosphere to obtain the aluminum nitride-yttrium oxide composite powder. According to the application, the aluminum nitride-yttrium oxide composite powder with high purity, small particles and a narrow distribution range can be obtained.

Description

Technical Field

[0001] This invention relates to the field of inorganic powder preparation, and in particular to a method for preparing aluminum nitride-yttrium oxide composite powder and its application. Background Technology

[0002] Aluminum nitride (ANT) possesses excellent properties such as high thermal conductivity, wide bandgap, electrical insulation, a coefficient of thermal expansion close to that of silicon, chemical resistance, and non-toxicity, making it one of the most ideal ceramic materials for heat dissipation substrates and electronic device packaging. It is widely used as a heat dissipation substrate for high-power LEDs, packaging material for high-power microwave and radio frequency devices, and infrared windows. A prerequisite for preparing high-quality ANT ceramics is the synthesis of ANT powder with high purity, small particle size, and good sintering activity.

[0003] The preparation methods of aluminum nitride powder include direct nitriding [Jiang Heng, Kang Zhijun, Xie Yuanfeng, et al. Preparation of aluminum nitride powder by direct nitriding of aluminum powder [J]. Rare Metals, 2013, 37(03): 396-400.], carbothermal reduction [Xiao Jin, Zhou Feng, Chen Yanbin. Process study on preparation of aluminum nitride powder by microwave carbothermal reduction [J]. Journal of Inorganic Materials, 2009, 24(04): 755-758.], chemical vapor deposition [Yang Songlin, Niu Peili, Yu Ronghai. Preparation and growth mechanism of necklace-shaped AlN nanowires by chemical vapor deposition [J]. Journal of the Chinese Ceramic Society, 2010, 38(07): 1297-1302.], and self-propagating high-temperature synthesis [Fu Renli, Chen Kexin, Zhou Heping, et al.]. Self-propagating high-temperature synthesis of aluminum nitride particles with regular crystalline morphology [J]. Journal of Inorganic Materials, 2004, (06): 1402-1406.

[0004] Yttrium oxide is one of the rare earth sesquioxides (Re2O3). It usually exists in three crystal forms: cubic, hexagonal and monoclinic. Below 2000℃, the cubic phase is the thermodynamically stable phase. Cubic yttrium oxide powder usually appears as a white powder with a slight yellow tint. Its physicochemical properties can be summarized as follows: high melting point, excellent chemical stability, wide wavelength transmittance, high light transmittance, cubic crystal structure and high thermal conductivity. Yttrium oxide is a commonly used sintering aid for aluminum nitride ceramics [Ma Xuegang, Kan Lianhe, Zhang Qingjun, et al. Research progress of sintering aids for aluminum nitride ceramics [J]. Shandong Ceramics, 2010, 33(04): 17-19; Wu Yubiao, Zhan Jun, Zhang Hao, et al. Research status of low temperature sintering aids for high thermal conductivity AlN ceramics [J]. China Ceramics, 2013, 49(09): 1-5.]. Yttrium oxide sintering aids possess advantages such as strong oxygen removal ability and good stability. During the sintering process of aluminum nitride ceramics, yttrium oxide combines with alumina impurities on the surface and inside the aluminum nitride particles to form one or more yttrium aluminates (Y3Al5O3).12 The second phase of aluminum nitride (YAlO3 and Y4Al2O9) can reduce the oxygen content in aluminum nitride grains and improve the thermal conductivity of aluminum nitride ceramics. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing aluminum nitride-yttrium oxide composite powder, which can improve the purity of aluminum nitride-yttrium oxide composite powder, reduce its particle size, and optimize its particle size distribution.

[0006] To address the above problems, this invention discloses a method for preparing aluminum nitride-yttrium oxide composite powder, comprising: (1) Using water as a dispersion medium, an aluminum source, a yttrium source, a carbon source, and a precipitant are dispersed therein and then subjected to a hydrothermal reaction to obtain a precursor; wherein, the carbon source is an organic compound that can be hydrothermally carbonized; the precipitant can generate hydroxide ions in the dispersion medium; the molar amount of Al in the aluminum source a, the molar amount of Y in the yttrium source y, and the molar amount of hydroxide ions generated by the precipitant q conform to the following relationship: (a+y) / q≤1 / 3; (2) The precursor is calcined in a nitrogen-containing atmosphere to obtain a nitrided product; wherein the calcination temperature is 1300~1600℃; (3) The nitrided product is subjected to decarbonization treatment in an oxygen-containing atmosphere to obtain aluminum nitride-yttrium oxide composite powder.

[0007] As an improvement to the above technical solution, the aluminum source is selected from one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, and aluminum acetate; The yttrium source is selected from one or more of yttrium nitrate, yttrium chloride, yttrium sulfate, and yttrium acetate. The carbon source is selected from one or more of starch, glucose, sucrose, fructose, maltose, lactose, chitosan, cellulose, dextrin, and cyclodextrin. The precipitant is selected from one or more of urea, ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, and hydrazine hydrate; The molar amount of Al in the aluminum source, a, the molar amount of Y in the yttrium source, and the molar amount of hydroxide ions generated by the precipitant, q, conform to the following relationship: (a+y): q=1: (3~8); The molar amount of Al, a, in the aluminum source and the molar amount of C, c, in the carbon source conform to the following relationship: a: c = 1: (3~7); The ratio of the total mass of the aluminum source, yttrium source, carbon source, and precipitant to the mass of water is (1~8): 10.

[0008] As an improvement to the above technical solution, the aluminum source is selected from aluminum nitrate, aluminum chloride, or aluminum acetate; The yttrium source is selected from yttrium nitrate, yttrium chloride, or yttrium acetate; The carbon source is selected from starch or sucrose; The precipitant is either urea or ammonia. The molar amount of Al in the aluminum source, a, the molar amount of Y in the yttrium source, and the molar amount of hydroxide ions generated by the precipitant, q, conform to the following relationship: (a+y): q=1: (3~4); The molar amount of Al, a, in the aluminum source and the molar amount of C, c, in the carbon source conform to the following relationship: a: c = 1: (3.3~4); The ratio of the total mass of the aluminum source, yttrium source, carbon source, and precipitant to the mass of water is (2~5): 10.

[0009] As an improvement to the above technical solution, in step (1), the temperature of the hydrothermal reaction is 140~220℃ and the heat preservation time is 2~24h; The heating rate of the hydrothermal reaction is 0.2~10℃ / min.

[0010] As an improvement to the above technical solution, in step (1), the temperature of the hydrothermal reaction is 180~200℃ and the heat preservation time is 4~8h; The heating rate of the hydrothermal reaction is 1~3℃ / min.

[0011] As an improvement to the above technical solution, in step (2), the nitrogen-containing atmosphere is selected from nitrogen atmosphere, mixed gas atmosphere of nitrogen and hydrogen, mixed gas atmosphere of nitrogen and rare gas or ammonia atmosphere. The calcination process is carried out according to the following temperature regime: Heat to 1300-1600℃ at a heating rate of 2-20℃ / min, and hold for 1-5 hours; Cool to 800-1000℃ at a cooling rate of 5-20℃ / min; Then it is allowed to cool to room temperature naturally.

[0012] As an improvement to the above technical solution, in step (2), the nitrogen-containing atmosphere is selected as a nitrogen atmosphere; The calcination process is carried out according to the following temperature regime: Heat to 1400-1500℃ at a heating rate of 5-10℃ / min, and hold for 2-3 hours; Cool to 800-1000℃ at a cooling rate of 5-10℃ / min; Then it is allowed to cool to room temperature naturally.

[0013] As an improvement to the above technical solution, in step (3), the oxygen-containing atmosphere is selected as an air atmosphere or an oxygen atmosphere; The decarbonization treatment is carried out according to the following temperature regime: Heat to 600-800℃ at a heating rate of 1-20℃ / min, and hold for 0.5-5 hours; Cool to 200-300℃ at a cooling rate of 5-10℃ / min; Then let it cool naturally to room temperature.

[0014] As an improvement to the above technical solution, step (1) includes: (1.1) Aluminum source, yttrium source, carbon source and precipitant are dispersed in water as a dispersion medium and then subjected to hydrothermal reaction; (1.2) The synthesis product obtained from the hydrothermal reaction was filtered, dried and sieved to obtain the precursor; In step (1.2), the filtration is gravity filtration or vacuum filtration; The drying process is either hot air drying or freeze-vacuum drying. Hot air drying involves a drying temperature of 40-80°C and a drying time of 6-24 hours. Freeze-vacuum drying involves a drying temperature of... 50~ 30℃, pressure 10~30Pa, drying time 6~24h; The sieve used during sieving has a mesh size of 80 to 250.

[0015] Accordingly, the present invention also discloses the application of the aluminum nitride-yttrium oxide composite powder prepared by the above-mentioned method in the preparation of aluminum nitride special ceramics, special ceramics containing aluminum nitride, or heat dissipation fillers.

[0016] Implementing this invention has the following beneficial effects: In one embodiment of the present invention, the preparation method of aluminum nitride-yttrium oxide composite powder involves subjecting an aluminum source, a yttrium source, a carbon source, and a precipitant to a hydrothermal reaction to obtain a precursor. The precursor is then calcined in a nitrogen-containing atmosphere and subjected to decarbonization treatment in an oxygen-containing atmosphere to obtain the aluminum nitride-yttrium oxide composite powder. The preparation method of the present invention can achieve uniform mixing of the carbon source, yttrium source, and aluminum source at the molecular level through solute dissolution, increasing the contact area between the three components. This effectively improves the reactivity and compositional uniformity of the precursor during the carbothermic reduction nitridation process, significantly enhancing the purity and distribution uniformity of the aluminum nitride-yttrium oxide composite powder, and reducing its particle size. Attached Figure Description

[0017] Figure 1 The XRD pattern of the aluminum nitride-yttrium oxide composite powder prepared in Example 1 of this invention; Figure 2 Here is a SEM image of the aluminum nitride-yttrium oxide composite powder prepared in Example 1 of this invention; Figure 3HAADF-STEM images of aluminum nitride-yttrium oxide composite powder prepared in Example 1 of this invention: (a) HAADF; (b) Al; (c) N; (d) Y; (e) O; Figure 4 The XRD pattern of the aluminum nitride-yttrium oxide composite powder prepared in Example 2 of this invention; Figure 5 Here is a SEM image of the aluminum nitride-yttrium oxide composite powder prepared in Example 2 of this invention; Figure 6 The image shows the XRD pattern of the aluminum nitride-yttrium oxide composite powder prepared in Comparative Example 1 of this invention. Detailed Implementation

[0018] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional range of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0020] The following embodiments are provided for the purpose of illustrating various embodiments of the present invention and are not intended to limit the invention in any way. Those skilled in the art will understand that variations and other uses as defined in the claims are included within the spirit and scope of the invention. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments are commercially available.

[0021] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0022] Unless otherwise specified, the percentage content involved in this invention refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0023] Unless otherwise specified, all percentage concentrations mentioned in this invention refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0024] Unless otherwise specified, the temperature parameters in this invention can be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument.

[0025] This invention discloses a method for preparing aluminum nitride-yttrium oxide composite powder, which includes the following steps: S1: Using water as a dispersion medium, aluminum source, yttrium source, carbon source and precipitant are dispersed in it and then subjected to a hydrothermal reaction to obtain the precursor; S2: The precursor is calcined in a nitrogen-containing atmosphere to obtain the nitrided product; S3: The nitrided product is subjected to decarbonization treatment in an oxygen-containing atmosphere to obtain aluminum nitride-yttrium oxide composite powder.

[0026] Based on the above preparation method, carbon source, yttrium source, and aluminum source can be uniformly mixed at the molecular level through solute dissolution, thereby increasing the contact area between the three and effectively improving the reactivity of the precursor in the carbothermic reduction nitridation process and the uniformity of the powder composition. This significantly improves the purity and distribution uniformity of the aluminum nitride-yttrium oxide composite powder and reduces its particle size.

[0027] Specifically, the aluminum source refers to a water-soluble or hydrolyzable aluminum salt, such as one or more of aluminum nitrate or its hydrate, aluminum chloride or its hydrate, aluminum sulfate or its hydrate, aluminum acetate, and aluminum bromide, but is not limited thereto. Preferably, in some embodiments, the aluminum source is one or more of aluminum nitrate or its hydrate, aluminum chloride or its hydrate, aluminum sulfate or its hydrate, and aluminum acetate. More preferably, the aluminum source is aluminum nitrate, aluminum nitrate hydrate, aluminum chloride, or aluminum chloride hydrate. These aluminum sources have high solubility in water, and using these highly soluble aluminum sources can significantly increase the precursor yield per unit space of the hydrothermal reactor.

[0028] Specifically, the yttrium source refers to a water-soluble or hydrolyzable yttrium salt, such as one or more of yttrium nitrate or its hydrate, yttrium chloride or its hydrate, yttrium sulfate or its hydrate, and yttrium acetate, but is not limited thereto. Preferably, in some embodiments, the yttrium source is one or more of yttrium nitrate or its hydrate, yttrium chloride or its hydrate, yttrium sulfate or its hydrate, and yttrium acetate. More preferably, the yttrium source is yttrium nitrate, yttrium nitrate hydrate, yttrium chloride, or yttrium chloride hydrate. These yttrium sources have high solubility in water, which can ensure the uniform distribution of the components in the precursor.

[0029] Specifically, a carbon source refers to an organic compound that can be dispersed in water and is hydrothermally carbonizable. For example, the carbon source may be one or more of starch, glucose, sucrose, fructose, maltose, lactose, chitosan, cellulose, dextrin, and cyclodextrin, but is not limited thereto. Preferably, the carbon source is starch or sucrose.

[0030] Specifically, the precipitant is a substance that can ionize in the dispersion medium to generate hydroxide ions or react with the dispersion medium to generate hydroxide ions. Exemplary examples include ammonia, urea, sodium hydroxide, potassium hydroxide, calcium hydroxide, hydrazine hydrate, and dimethylamine, but it is not limited to these. Preferably, in some embodiments, the precipitant is one or more of urea, ammonia, and hydrazine hydrate. More preferably, the precipitant is urea or ammonia. The concentration of ammonia is 25-28 wt.%.

[0031] Taking urea as an example, it undergoes a hydrolysis reaction during the hydrothermal reaction process. 1 mol of urea will form 2 mol of hydroxide ions. The specific chemical reaction process is shown in the following formula.

[0032]

[0033] Specifically, during the hydrothermal reaction, the hydroxide ions generated by the precipitant combine with the aluminum ions and yttrium ions generated by the aluminum source, and combine with the carbon particles generated by the hydrothermal carbonization of the carbon source to form a precursor in which aluminum hydroxy oxide, yttrium hydroxy oxide and carbon particles are uniformly mixed. This lays a good foundation for the subsequent preparation of high-purity, small-particle-size aluminum nitride-yttrium oxide composite powder.

[0034] Specifically, in order to completely convert aluminum in the aluminum source and yttrium in the yttrium source, the molar number of hydroxide ions generated by the precipitant should be controlled to be greater than three times the sum of the molar amounts of aluminum in the aluminum source and yttrium in the yttrium source. Preferably, in some embodiments, the molar amount of Al (a) in the aluminum source, the molar amount of Y (y) in the yttrium source, and the molar amount of hydroxide ions (q) generated by the precipitant conform to the following relationship: (a+y): q = 1: (3~8); exemplary values ​​are 1: 3.6, 1: 4.4, 1: 5.2, 1: 6.0, 1: 7.2, or 1: 7.6, but are not limited thereto. More preferably, (a+y): q = 1: (3.3~4).

[0035] Specifically, to improve the conversion rate of Al to AlN in the aluminum source, the molar amount of Al in the aluminum source needs to be controlled to be lower than the molar amount of C in the carbon source. Preferably, in some embodiments, the molar amount of Al 'a' in the aluminum source and the molar amount of C 'c' in the carbon source conform to the following relationship: a:c = 1: (3~7); exemplary ratios are 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, or 1:6.5, but are not limited thereto. More preferably, a:c = 1: (3.3~4).

[0036] Specifically, this invention does not impose explicit restrictions on the molar ratio of Al in the aluminum source and Y in the yttrium source. Those skilled in the art can select a suitable ratio according to the application requirements of the composite powder. For example, the ratio a:y between the molar amount of Al in the aluminum source (a) and the molar amount of Y in the yttrium source (y) can be 0.1:1, 0.5:1, 1:1, 1:0.5, 1:0.1, 1:0.05, or 1:0.01, but is not limited thereto.

[0037] Specifically, in step S1, to ensure the hydrothermal reaction proceeds uniformly and fully, the mass ratio of the total mass of the aluminum source, yttrium source, carbon source, and precipitant to the mass of water is controlled to be (1~8): 10, exemplarily 1.5: 10, 2.3: 10, 3.5: 10, 4: 10, or 4.6: 10, but not limited thereto. More preferably, the mass ratio of the total mass of the aluminum source, yttrium source, carbon source, and precipitant to the mass of water is (2~5): 10.

[0038] Specifically, in step S1, the hydrothermal reaction temperature is 140~220℃, exemplarily 150℃, 170℃, 190℃, or 210℃, but not limited thereto. Preferably, it is 180~200℃. The holding time of the hydrothermal reaction (i.e., the duration at the highest temperature) is 2~24h, exemplarily 2.5h, 5h, 7.5h, 10h, 12.5h, 15h, 17.5h, 20h, or 22.5h, but not limited thereto. Preferably, it is 4~8h. The heating rate of the hydrothermal reaction is 0.2~10℃ / min, exemplarily 0.5℃ / min, 1.5℃ / min, 4℃ / min, 5.5℃ / min, 7℃ / min, 8.5℃ / min, or 9℃ / min, but not limited thereto. Preferably, it is 1~3℃ / min. Based on the above-mentioned reaction temperature, heating rate, and reaction time, a precursor consisting of a uniform mixture of aluminum hydroxyl oxide, yttrium hydroxyl oxide, and carbon particles can be formed. This precursor has the advantages of small particle size, narrow particle size distribution, and low particle agglomeration.

[0039] Preferably, in some embodiments, step S1 includes: S11: Aluminum source, yttrium source, carbon source and precipitant are dispersed in water as a dispersion medium and then subjected to hydrothermal reaction. Specifically, in some implementations, an aluminum source, a yttrium source, a carbon source, and a precipitant are added to water, stirred until completely dissolved, and then a hydrothermal reaction is carried out.

[0040] S12: The precursor is obtained by filtering, drying and sieving the synthetic product obtained by hydrothermal reaction; Specifically, in some embodiments, solid-liquid separation is achieved through gravity filtration, vacuum filtration, or pressure filtration, but is not limited to these methods. Gravity filtration or vacuum filtration is preferred. This invention uses water as the dispersion medium, enabling solid-liquid separation through simple filtration, thus simplifying the operation.

[0041] Specifically, in some implementation methods, the drying is either hot air convection drying or freeze-vacuum drying. Hot air convection drying involves a drying temperature of 40-80°C and a drying time of 6-24 hours; freeze-vacuum drying involves a drying temperature of... 50~ Drying temperature: 30℃, pressure: 10~30Pa, drying time: 6~24h.

[0042] Specifically, in some implementation methods, the mesh size of the sieve used during screening is 80 to 250 mesh.

[0043] Specifically, in step S2, when the temperature is increased in a nitrogen-containing atmosphere, aluminum hydroxy oxide and yttrium hydroxy oxide first dehydrate and transform into homogeneous oxides with uniformly distributed aluminum and yttrium. Then, the aluminum oxide component undergoes a carbothermic reduction nitriding reaction with carbon particles to form aluminum nitride. The specific reaction process is shown in the following formula.

[0044]

[0045] Since the carbothermic formation temperature of yttrium oxide to yttrium nitride (≥1600℃) is much higher than the nitriding temperature of alumina (≥1300℃), yttrium oxide will not undergo nitriding during the formation of aluminum nitride. Furthermore, because the carbon particles, aluminum hydroxyl oxide, and yttrium hydroxyl oxide are uniformly combined in this invention, a transitional reaction occurs during the carbothermic reduction nitriding of alumina, forming yttrium aluminate with yttrium oxide (see Comparative Example 1). After the yttrium aluminate is consumed, only aluminum nitride, yttrium oxide, and residual carbon remain in the system. Since aluminum nitride and yttrium oxide do not react to form a eutectic phase below 1942℃, during the cooling process after calcination, yttrium oxide will eventually separate from aluminum nitride, forming two powder particles with completely different phases and compositions.

[0046] Specifically, in step S2, the nitrogen-containing atmosphere is a nitrogen atmosphere, a mixture of nitrogen and hydrogen, a mixture of nitrogen and rare gases, or an ammonia atmosphere, but is not limited to these. Preferably, it is a pure nitrogen atmosphere.

[0047] Specifically, in step S2, the calcination temperature is 1300~1600℃, exemplarily 1350℃, 1400℃, 1450℃, 1500℃, or 1550℃, but not limited thereto. Preferably, it is 1400~1500℃. The calcination holding time (i.e., the time maintained at the highest calcination temperature) is 1~5h, exemplarily 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, or 4.5h, but not limited thereto. Preferably, it is 2~3h. The precursor of the present invention can effectively reduce the calcination temperature.

[0048] Preferably, in some embodiments, the calcination process is carried out according to the following temperature regime: Heat to 1300-1600℃ at a heating rate of 2-20℃ / min, and hold for 1-5 hours; Cool to 800-1000℃ at a cooling rate of 5-20℃ / min; Then, the product is allowed to cool to room temperature naturally. Natural cooling refers to placing the calcined product in a calcination device (such as a muffle furnace) and allowing it to cool as the temperature of the calcination device decreases without applying other cooling methods (such as blowing air or opening the furnace door).

[0049] More preferably, in some embodiments, the calcination process is carried out according to the following temperature regime: Heat to 1400-1500℃ at a heating rate of 5-10℃ / min, and hold for 2-3 hours; Cool to 800-1000℃ at a cooling rate of 5-10℃ / min; Then it is allowed to cool to room temperature naturally.

[0050] Specifically, in step S3, the oxygen-containing atmosphere is either an air atmosphere or an oxygen atmosphere, but is not limited to these. Preferably, an air atmosphere is used.

[0051] Specifically, in step S3, the roasting temperature for decarbonization is 600~850℃, exemplarily 640℃, 670℃, 700℃, 730℃, 760℃, 790℃ or 820℃, but not limited thereto. Preferably, it is 600~800℃.

[0052] Preferably, in some embodiments, the decarbonization treatment is carried out according to the following temperature regime: Heat to 600-800℃ at a heating rate of 1-20℃ / min, and hold for 0.5-5 hours; Cool to 200-300℃ at a cooling rate of 5-10℃ / min; Then let it cool naturally to room temperature.

[0053] Through the above-described decarbonization process, residual carbon particles can be completely oxidized and removed, resulting in high-purity aluminum nitride-yttrium oxide composite powder. The aluminum nitride-yttrium oxide composite powder of this invention can be used directly as a powder, for example, exhibiting excellent thermal conductivity and heat dissipation after being composited with epoxy resin, making it suitable as an encapsulation material for electronic products; it can also be applied to sintering special ceramics, such as directly sintering aluminum nitride special ceramics as substrate materials, high-temperature structural materials, corrosion-resistant refractory materials, etc.; or used as a sintering aid for difficult-to-sinter ceramics such as silicon carbide; it can also be directly used in sintering composite ceramics, such as aluminum nitride-yttrium oxide multiphase ceramics, etc.

[0054] The present invention will be further illustrated below with specific embodiments. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available or can be prepared by known methods. In the embodiments, XRD spectra were obtained using an X-ray diffractometer (Miniflex-600, Rigaku). TEM images were taken using a transmission electron microscope (FEI Tecnai G2F20, Hillsboro). SEM images were obtained using a scanning electron microscope (SU 8010 & Regulus 8100, Hotachi).

[0055] Example 1 (1) The starting materials were aluminum nitrate nonahydrate, yttrium nitrate hexahydrate, sucrose, and urea. According to the molar ratio, yttrium nitrate: aluminum nitrate = 0.0229: 1, urea: (aluminum nitrate + yttrium nitrate) = 2: 1, and the molar ratio of carbon in sucrose to aluminum nitrate Al: C = 1: 4, the above materials were weighed and placed in the same beaker. Then, deionized water was added to the beaker according to the mass ratio of solvent: solute = 10: 3, and the mixture was stirred with a magnetic stirrer until all reagents were completely dissolved.

[0056] (2) The mixture obtained in step (1) was transferred to a polytetrafluoroethylene liner and placed in a stainless steel reactor. It was then placed in a constant-temperature drying oven and heated from room temperature to 200°C at a rate of 1°C / min for 8 hours, and then cooled to room temperature. Next, the reaction product was poured into a Buchner funnel and vacuum filtered on a suction flask. The obtained precursor was placed in a constant-temperature drying oven and dried at 60°C for 6 hours, and then passed through a 100-mesh sieve.

[0057] (3) Transfer the precursor powder obtained in step (2) to a boron nitride crucible and place it in a graphite furnace. Then, evacuate the graphite furnace and fill it with nitrogen. Raise the temperature from room temperature to 1500°C at a rate of 10°C / min and hold for 3 hours. Then lower the temperature to 1000°C at a rate of 10°C / min and allow it to cool naturally to room temperature.

[0058] (4) Transfer the calcined product obtained in step (3) to an alumina crucible and place it in a muffle furnace for calcination to remove carbon. Increase the temperature from room temperature to 700°C at a rate of 5°C / min and hold for 30 min. Then decrease the temperature to 250°C at a rate of 10°C / min and finally allow it to cool naturally to room temperature.

[0059] See Figure 1 The figure shows the XRD pattern of the aluminum nitride-yttrium oxide composite powder prepared in this embodiment. As can be seen from the figure, the aluminum nitride-yttrium oxide composite powder contains AlN and Y2O3 (which are consistent with standard cards JCPDS NO.76-0720 and JCPDS NO.41-1105, respectively), without other impurities. Moreover, its diffraction peak intensity is very high and the peak shape is good, indicating that its purity is very high.

[0060] See Figure 2 The image shows a SEM image of the aluminum nitride-yttrium oxide composite powder prepared in this embodiment. It can be seen from the image that the obtained aluminum nitride-yttrium oxide composite powder has a small particle size and a narrow distribution range.

[0061] Figure 3 This is a HAADF-STEM image (high-angle annular dark-field scanning transmission electron microscope) of the aluminum nitride-yttrium oxide composite powder prepared in this embodiment. Figure 3 (a) is a HAADF image, while Figure 3 (b), 3(c), 3(d), and 3(e) are the elemental distribution maps of Al, N, Y, and O, respectively. HAADF-STEM technology can generate high-resolution atomic number (Z) contrast images by detecting high-angle scattered electrons. Because yttrium and oxygen have high atomic numbers in the aluminum nitride-yttrium oxide composite powder, they are... Figure 3 In the HAADF image of (a), yttrium oxide particles appear light-colored, while aluminum nitride particles appear dark-colored. As can be seen from the image, spherical yttrium oxide particles of approximately 50 nm in size are uniformly attached to the surface of aluminum nitride particles of approximately 150 nm in diameter in the composite powder.

[0062] Example 2 (1) The starting materials were aluminum nitrate nonahydrate, yttrium nitrate hexahydrate, sucrose, and urea. According to the molar ratios of yttrium nitrate:aluminum nitrate = 0.0153:1, urea:(aluminum nitrate + yttrium nitrate) = 2:1, and the molar ratio of carbon in sucrose to aluminum nitrate Al:C = 1:4, the above materials were weighed and placed in the same beaker. Then, deionized water was added to the beaker according to a solvent:solute mass ratio of 10:3, and the mixture was stirred using a magnetic stirrer until the reagents were completely dissolved.

[0063] (2) The mixture obtained in step (1) was transferred to a polytetrafluoroethylene liner and then placed into a stainless steel reactor. It was then placed in a constant temperature drying oven and heated from room temperature to 200°C at a rate of 2°C / min and held at that temperature for 6 hours, before being cooled to room temperature. The reaction product was then poured into a Buchner funnel and vacuum filtered on a suction flask. The resulting precursor was placed in a constant temperature drying oven and dried at 60°C for 6 hours, then passed through an 80-mesh sieve.

[0064] (3) The precursor powder obtained in step (2) is transferred to a boron nitride crucible and placed in a graphite furnace. Then, the graphite furnace is evacuated and then filled with nitrogen. The temperature is increased from room temperature to 1400°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 800°C at a rate of 10°C / min and then cooled to room temperature with the furnace.

[0065] (4) Transfer the calcined product obtained in step (3) to an alumina crucible and place it in a muffle furnace for decarburization treatment. Increase the temperature from room temperature to 700°C at a rate of 5°C / min and hold for 30 min. Then decrease the temperature to 250°C at a rate of 10°C / min and finally allow it to cool naturally to room temperature.

[0066] See Figure 4 The figure shows the XRD pattern of the aluminum nitride-yttrium oxide composite powder prepared in this embodiment. As can be seen from the figure, the aluminum nitride-yttrium oxide composite powder contains AlN and Y2O3 (which are consistent with standard cards JCPDS NO.76-0720 and JCPDS NO.41-1105, respectively), and does not contain other impurities. Moreover, its diffraction peaks have high intensity and good shape, indicating that its purity is high.

[0067] See Figure 5 The image shows a SEM image of the aluminum nitride-yttrium oxide composite powder prepared in this embodiment. It can be seen from the image that the obtained aluminum nitride-yttrium oxide composite powder has a small particle size and a narrow distribution range.

[0068] Example 3 (1) The starting materials are aluminum nitrate nonahydrate, yttrium nitrate hexahydrate, sucrose, and ammonia (1 mol / L standard ammonia solution). According to the molar ratio, yttrium nitrate:aluminum nitrate = 1:1, ammonia:(aluminum nitrate + yttrium nitrate) = 3:1, and the molar ratio of carbon in sucrose to aluminum nitrate Al:C = 1:3.3. Weigh the above materials and place them in the same beaker. Then, add deionized water to the beaker according to the mass ratio of solvent:solute = 10:2, and stir with a magnetic stirrer until the reagents are completely dissolved.

[0069] (2) The mixture obtained in step (1) was transferred to a polytetrafluoroethylene liner and then placed into a stainless steel reactor. It was then placed in a constant temperature drying oven and heated from room temperature to 200°C at a rate of 2°C / min and held at that temperature for 4 hours, before being cooled to room temperature. The reaction product was then poured into a Buchner funnel and vacuum filtered on a suction flask. The resulting precursor was placed in a constant temperature drying oven and dried at 60°C for 6 hours, then passed through a 100-mesh sieve.

[0070] (3) Transfer the precursor powder obtained in step (2) into a boron nitride crucible and place it in a graphite furnace. Then, evacuate the graphite furnace and fill it with nitrogen. Raise the temperature from room temperature to 1500°C at a rate of 10°C / min and hold for 3 hours, then lower the temperature to 1000°C at a rate of 10°C / min. Then, allow it to cool to room temperature with the furnace.

[0071] (4) Transfer the calcined product obtained in step (3) to an alumina crucible and place it in a muffle furnace for decarburization treatment. Increase the temperature from room temperature to 700°C at a rate of 5°C / min and hold for 30 min, then decrease the temperature to 250°C at a rate of 10°C / min. Finally, allow it to cool naturally to room temperature to obtain aluminum nitride-yttrium oxide composite powder.

[0072] The resulting aluminum nitride-yttrium oxide composite powder has a small particle size and a narrow distribution range.

[0073] Example 4 (1) The starting materials are aluminum nitrate nonahydrate, yttrium nitrate hexahydrate, starch, and urea. According to the molar ratio, yttrium nitrate:aluminum nitrate = 1:1, urea:(aluminum nitrate + yttrium nitrate) = 1.5:1, and the molar ratio of carbon in starch to aluminum nitrate Al:C = 1:3.7, the above materials are weighed and placed in the same beaker. Then, deionized water is added to the beaker according to the mass ratio of solvent:solute = 10:2, and the mixture is heated and stirred with a magnetic stirrer until the reagents are completely dissolved.

[0074] (2) The mixture obtained in step (1) was transferred to a polytetrafluoroethylene liner and then placed into a stainless steel reactor. It was then placed in a constant temperature drying oven and heated from room temperature to 180°C at a rate of 2°C / min and held at that temperature for 8 hours, before being cooled to room temperature. The reaction product was then poured into a Buchner funnel and vacuum filtered on a suction flask. The resulting precursor was placed in a constant temperature drying oven and dried at 60°C for 6 hours, then passed through a 100-mesh sieve.

[0075] (3) Transfer the precursor powder obtained in step (2) into a boron nitride crucible and place it in a graphite furnace. Then, evacuate the graphite furnace and fill it with nitrogen. Raise the temperature from room temperature to 1500°C at a rate of 10°C / min and hold for 2 hours, then lower the temperature to 1000°C at a rate of 10°C / min. Then, allow it to cool to room temperature with the furnace.

[0076] (4) Transfer the calcined product obtained in step (3) to an alumina crucible and place it in a muffle furnace for decarburization treatment. Increase the temperature from room temperature to 700°C at a rate of 5°C / min and hold for 30 min, then decrease the temperature to 250°C at a rate of 10°C / min. Finally, allow it to cool naturally to room temperature to obtain aluminum nitride-yttrium oxide composite powder.

[0077] The resulting aluminum nitride-yttrium oxide composite powder has a small particle size and a narrow distribution range.

[0078] Comparative Example 1 (1) The starting materials were aluminum nitrate nonahydrate, yttrium nitrate hexahydrate, sucrose, and urea. According to the molar ratio, yttrium nitrate:aluminum nitrate = 0.0229:1, urea:(aluminum nitrate + yttrium nitrate) = 2:1, and the molar ratio of carbon in sucrose to aluminum nitrate Al:C = 1:4, the above materials were weighed and placed in the same beaker. Then, deionized water was added to the beaker according to the mass ratio of solvent:solute = 10:3, and the mixture was stirred with a magnetic stirrer until all reagents were completely dissolved.

[0079] (2) The mixture obtained in step (1) was transferred to a polytetrafluoroethylene liner and placed in a stainless steel reactor. It was then placed in a constant-temperature drying oven and heated from room temperature to 200°C at a rate of 1°C / min for 8 hours, and then cooled to room temperature. Next, the reaction product was poured into a Buchner funnel and vacuum filtered on a suction flask. The obtained precursor was placed in a constant-temperature drying oven and dried at 60°C for 6 hours, and then passed through a 100-mesh sieve.

[0080] (3) The precursor powder obtained in step (2) is transferred to a boron nitride crucible and placed in a graphite furnace. Then, the graphite furnace is evacuated and then filled with nitrogen. The temperature is increased from room temperature to 1300°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 1000°C at a rate of 10°C / min and then cooled to room temperature with the furnace.

[0081] (4) Transfer the calcined product obtained in step (3) to an alumina crucible and place it in a muffle furnace for calcination to remove carbon. Increase the temperature from room temperature to 700°C at a rate of 5°C / min and hold for 30 min. Then decrease the temperature to 250°C at a rate of 10°C / min and finally allow it to cool naturally to room temperature.

[0082] See Figure 6 The figure shows the XRD pattern of the aluminum nitride-yttrium oxide composite powder prepared in this comparative example. It can be seen from the figure that the calcined product powder contains AlN, γAl₂O₃ and YAlO₃ (corresponding to standard cards JCPDS NO.76-0720, JCPDS NO.50-0741, and JCPDS NO.74-1334, respectively) are not pure aluminum nitride-yttrium oxide composite powders. Furthermore, this comparative example shows that the precursors undergo a transition to a yttrium aluminate (YAlO₃) mesophase during nitridation before finally yielding AlN and Y₂O₃.

[0083] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of the present invention to facilitate a specific and detailed understanding of the technical solution of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0084] It should be understood that any technical solutions obtained by those skilled in the art based on the technical solutions provided in this invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing aluminum nitride-yttrium oxide composite powder, characterized in that, include: (1) Using water as a dispersion medium, an aluminum source, a yttrium source, a carbon source, and a precipitant are dispersed therein and then subjected to a hydrothermal reaction to obtain a precursor; wherein, the carbon source is an organic compound that can be hydrothermally carbonized; the precipitant can generate hydroxide ions in the dispersion medium; the molar amount of Al in the aluminum source a, the molar amount of Y in the yttrium source y, and the molar amount of hydroxide ions generated by the precipitant q conform to the following relationship: (a+y) / q≤1 / 3; (2) The precursor is calcined in a nitrogen-containing atmosphere to obtain a nitrided product; wherein the calcination temperature is 1300~1600℃; (3) The nitrided product is subjected to decarbonization treatment in an oxygen-containing atmosphere to obtain aluminum nitride-yttrium oxide composite powder.

2. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, The aluminum source is selected from one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, and aluminum acetate; The yttrium source is selected from one or more of yttrium nitrate, yttrium chloride, yttrium sulfate, and yttrium acetate. The carbon source is selected from one or more of starch, glucose, sucrose, fructose, maltose, lactose, chitosan, cellulose, dextrin, and cyclodextrin. The precipitant is selected from one or more of urea, ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, and hydrazine hydrate; The molar amount of Al in the aluminum source, a, the molar amount of Y in the yttrium source, and the molar amount of hydroxide ions generated by the precipitant, q, conform to the following relationship: (a+y): q=1: (3~8); The molar amount of Al, a, in the aluminum source and the molar amount of C, c, in the carbon source conform to the following relationship: a: c = 1: (3~7); The ratio of the total mass of the aluminum source, yttrium source, carbon source, and precipitant to the mass of water is (1~8):

10.

3. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, The aluminum source is selected from aluminum nitrate, aluminum chloride, or aluminum acetate. The yttrium source is selected from yttrium nitrate, yttrium chloride, or yttrium acetate; The carbon source is selected from starch or sucrose; The precipitant is either urea or ammonia. The molar amount of Al in the aluminum source, a, the molar amount of Y in the yttrium source, and the molar amount of hydroxide ions generated by the precipitant, q, conform to the following relationship: (a+y): q=1: (3~4); The molar amount of Al, a, in the aluminum source and the molar amount of C, c, in the carbon source conform to the following relationship: a: c = 1: (3.3~4); The ratio of the total mass of the aluminum source, yttrium source, carbon source, and precipitant to the mass of water is (2~5):

10.

4. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, In step (1), the temperature of the hydrothermal reaction is 140~220℃, and the holding time is 2~24h; The heating rate of the hydrothermal reaction is 0.2~10℃ / min.

5. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, In step (1), the temperature of the hydrothermal reaction is 180~200℃, and the holding time is 4~8h; The heating rate of the hydrothermal reaction is 1~3℃ / min.

6. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, In step (2), the nitrogen-containing atmosphere is selected from nitrogen atmosphere, mixed gas atmosphere of nitrogen and hydrogen, mixed gas atmosphere of nitrogen and rare gas or ammonia atmosphere. The calcination process is carried out according to the following temperature regime: Heat to 1300-1600℃ at a heating rate of 2-20℃ / min, and hold for 1-5 hours; Cool to 800-1000℃ at a cooling rate of 5-20℃ / min; Then it is allowed to cool to room temperature naturally.

7. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, In step (2), the nitrogen-containing atmosphere is a nitrogen atmosphere; The calcination process is carried out according to the following temperature regime: Heat to 1400-1500℃ at a heating rate of 5-10℃ / min, and hold for 2-3 hours; Cool to 800-1000℃ at a cooling rate of 5-10℃ / min; Then it is allowed to cool to room temperature naturally.

8. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, In step (3), the oxygen-containing atmosphere is selected from air atmosphere or oxygen atmosphere; The decarbonization treatment is carried out according to the following temperature regime: Heat to 600-800℃ at a heating rate of 1-20℃ / min, and hold for 0.5-5 hours; Cool to 200-300℃ at a cooling rate of 5-10℃ / min; Then let it cool naturally to room temperature.

9. The method for preparing aluminum nitride-yttrium oxide composite powder as described in claim 1, characterized in that, Step (1) includes: (1.1) Aluminum source, yttrium source, carbon source and precipitant are dispersed in water as a dispersion medium and then subjected to hydrothermal reaction; (1.2) The synthesis product obtained from the hydrothermal reaction was filtered, dried and sieved to obtain the precursor; In step (1.2), the filtration is gravity filtration or vacuum filtration; The drying process is either hot air drying or freeze-vacuum drying. Hot air drying involves a drying temperature of 40-80°C and a drying time of 6-24 hours. Freeze-vacuum drying involves a drying temperature of... 50~ 30℃, pressure 10~30Pa, drying time 6~24h; The sieve used during sieving has a mesh size of 80 to 250.

10. The application of the aluminum nitride-yttrium oxide composite powder prepared by the method of any one of claims 1 to 9 in the preparation of aluminum nitride special ceramics, special ceramics containing aluminum nitride, or heat dissipation fillers.

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