Silicon nitride ceramic powder and preparation method thereof

Abstract

The invention relates to the field of ceramic material preparation, in particular to silicon nitride ceramic powder and a preparation method thereof.The preparation method comprises the following steps that S1, silicon powder and a catalyst are mixed and subjected to high-energy ball milling refining to obtain a silicon nitride reactant, the catalyst is selected from one or more of rare earth oxides, and the rare earth oxides are selected from one or more of rare earth oxides; the content of the catalyst in the silicon nitride reactant is 1-10 wt%; and S2, carrying out direct nitridation reaction on the silicon nitride reactant to obtain the silicon nitride ceramic powder. The silicon powder is refined through high-energy ball milling, so that the reaction efficiency and the reaction activity are improved, the reaction temperature is reduced by adding the rare earth oxide, and the reaction efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of ceramic material preparation, and in particular to a silicon nitride ceramic powder and a preparation method thereof. Background Art

[0002] Silicon nitride (Si3N4) has the characteristics of high strength, high hardness, strong corrosion resistance, strong wear resistance, and strong oxidation resistance. It is widely used in super-hard, corrosion-resistant and wear-resistant parts, refractory materials, engine and gas turbine parts, high-speed cutting tools and other fields. In recent years, with the continuous development of high-power devices, traditional PCB boards cannot meet the application needs, making ceramic substrates show a good development momentum. As one of the four traditional ceramic materials, silicon nitride is also considered to have the basic properties required by ceramic substrates. Similar to aluminum nitride, silicon nitride powder also needs to be artificially synthesized. At present, the preparation methods of silicon nitride powder mainly include ammonia solution, carbon thermal reduction, direct nitridation and combustion, while industrial production mainly adopts carbon thermal reduction and direct nitridation. Among them, direct nitridation is the first choice for large-scale production. However, the current problems of direct nitridation include high reaction temperature and high energy consumption, which result in high product cost. The main reason is that it is not conducive to the diffusion of nitrogen in the molten state of silicon, resulting in low nitridation efficiency. The currently recognized solution is to use a catalyst. Although the catalyst can be metal or oxide, oxide has better comprehensive effect. However, the catalytic efficiency of existing oxide catalysts is low. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of low nitridation efficiency of preparing silicon nitride by direct nitridation method in the prior art. A silicon nitride ceramic powder and a preparation method thereof are proposed. The preparation method of the silicon nitride ceramic powder has simple steps, high reaction activity and high reaction efficiency.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing silicon nitride ceramic powder, the method for preparing silicon nitride ceramic powder comprising the following steps:

[0005] S1. Mixing silicon powder and a catalyst and subjecting them to high-energy ball milling to obtain a silicon nitride reactant, wherein the catalyst is selected from one or more rare earth oxides, and the content of the catalyst in the silicon nitride reactant is 1-10 wt %;

[0006] S2. Directly nitriding the silicon nitride reactant to obtain silicon nitride ceramic powder, wherein the reaction temperature of the direct nitridation reaction is 1300-1900°C.

[0007] Furthermore, the high-energy ball milling in step S1 is a dry milling process, using carbide grinding balls for ball milling, the carbide grinding balls have a diameter of 1-10 mm, the ball-to-material mass ratio is (40-20): 1, the ball milling rate is 100-300 rpm, the ball milling time is 2-24 h, and the ball milling is stopped for 5-10 min every 0.5-1 h during the ball milling process.

[0008] Furthermore, the cemented carbide grinding balls are tungsten carbide grinding balls with a diameter of 10 mm, a ball-to-material mass ratio of 40:1, a ball milling rate of 200 rpm, a ball milling time of 12 h, and the ball milling is stopped for 5 min every 0.5 h during the ball milling process.

[0009] In the above technical solution, silicon powder will release a lot of heat during high-energy ball milling. It is necessary to set the pause parameters according to the heating situation, that is, stop the ball milling for 5-10 minutes every 0.5-1h during the ball milling process. Preferably, stop the ball milling for 5 minutes every 0.5h during the ball milling process.

[0010] Furthermore, the direct nitridation reaction in step S2 is carried out under a flowing atmosphere, the flowing atmosphere is nitrogen and / or ammonia, and the gas flow rate of the flowing atmosphere is 0.5-2.5 L / min.

[0011] Furthermore, the reaction temperature of the direct nitridation reaction in step S2 is 1500-1600° C., and the reaction time is 4-24 hours.

[0012] Furthermore, the reaction temperature of the direct nitridation reaction in step S2 is 1580° C., and the reaction time is 8 h.

[0013] Furthermore, the catalyst in step S1 is selected from one or more of yttrium oxide, lanthanum oxide, neodymium oxide, samarium oxide, europium oxide, dysprosium oxide, and erbium oxide.

[0014] Furthermore, the catalyst is yttrium oxide.

[0015] Furthermore, the content of the catalyst in the silicon nitride reactant is 3-5%.

[0016] Furthermore, the silicon powder is selected from commercial silicon powder, scraps, defective products, and residual silicon of solar energy or semiconductors.

[0017] Silicon nitride ceramic powder prepared by the above-mentioned method for preparing silicon nitride ceramic powder.

[0018] The silicon nitride ceramic powder can be used to prepare silicon nitride ceramic packaging substrates, various silicon nitride ceramic structural parts, silicon nitride thermal conductive fillers, etc.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention adopts high-energy ball milling process to grind and refine silicon powder and catalyst, thereby improving reaction activity and reaction efficiency;

[0021] 2. The present invention finds that rare earth oxides can not only be used as sintering aids for silicon nitride ceramics, but also as catalysts for the preparation of silicon nitride ceramic powders by direct nitridation. The use of rare earth oxides as catalysts can not only reduce the reaction temperature to as low as 1580°C, but also improve the reaction efficiency and activity.

[0022] 3. The present invention can prepare silicon nitride ceramic powder in only two steps. The preparation method is simple, the raw material silicon powder has a wide source, and waste materials can be used. It conforms to the concept of sustainable development and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Figure 1 is the X-ray diffraction (XRD) pattern of the silicon nitride reactant prepared in Example 1 before and after ball milling, wherein Al2O3 is an artificially added standard reference, WC is a cemented carbide impurity introduced by ball milling, and WC evaporates and disappears during the subsequent high-temperature reaction process. (a) is before ball milling, and (b) is after ball milling. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] The present invention is now further described in conjunction with specific examples. The following examples are only for explaining the present invention, but do not constitute a limitation of the present invention. The test samples and test processes used in the following examples include the following (if the specific experimental conditions are not indicated in the examples, they are usually in accordance with conventional conditions or the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following examples, if not otherwise specified, can all be obtained from commercial channels).

[0027] Example 1

[0028] A method for preparing silicon nitride ceramic powder, the preparation method comprising:

[0029] S1. By weight, 99 parts of commercial silicon powder and 1 part of yttrium oxide (Y2O3) powder are mixed evenly, and the mixed powder is subjected to high-energy refinement to obtain a silicon nitride reactant.

[0030] The high-energy ball milling adopts dry grinding process, uses carbide grinding balls for high-energy ball milling, the carbide grinding balls have a diameter of 10 mm, the ball-to-material mass ratio is 40:1, the ball milling rate is 200 rpm, the high-energy ball milling time is 12 h, and the ball milling is stopped for 5 min every 0.5 h during the high-energy ball milling process;

[0031] S2, subjecting the silicon nitride reactant obtained in step S1 to direct catalytic nitridation to obtain silicon nitride ceramic powder,

[0032] The specific conditions of direct catalytic nitridation treatment are: reacting in a high-purity nitrogen flowing atmosphere, the gas flow rate of the flowing atmosphere is 1.5L / min, the reaction temperature is 1600°C, the reaction time is 8h, and the furnace is cooled down after the reaction is completed.

[0033] Example 2

[0034] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 97 parts of commercial silicon powder and 3 parts of yttrium oxide (Y2O3) powder are uniformly mixed.

[0035] Example 3

[0036] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 95 parts of commercial silicon powder and 5 parts of yttrium oxide (Y2O3) powder are uniformly mixed.

[0037] Example 4

[0038] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 93 parts of commercial silicon powder and 7 parts of yttrium oxide (Y2O3) powder are uniformly mixed.

[0039] Example 5

[0040] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 90 parts of commercial silicon powder and 10 parts of yttrium oxide (Y2O3) powder are uniformly mixed.

[0041] Example 6

[0042] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 99 parts of commercial silicon powder and 1 part of lanthanum oxide (La2O3) powder are uniformly mixed.

[0043] Example 7

[0044] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 99 parts of commercial silicon powder and 1 part of neodymium oxide (Nd2O3) powder are uniformly mixed.

[0045] Example 8

[0046] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 99 parts of commercial silicon powder and 1 part of samarium oxide (Sm2O3) powder are uniformly mixed.

[0047] Example 9

[0048] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 99 parts of commercial silicon powder and 1 part of europium oxide (Eu2O3) powder are uniformly mixed.

[0049] Example 10

[0050] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 99 parts of commercial silicon powder and 1 part of dysprosium oxide (Dy2O3) powder are uniformly mixed.

[0051] Embodiment 11

[0052] A method for preparing silicon nitride ceramic powder is the same as that of Example 1, except that in step S1, 99 parts of commercial silicon powder and 1 part of erbium oxide (Er2O3) powder are uniformly mixed.

[0053] Example 12

[0054] A method for preparing silicon nitride ceramic powder, the preparation method comprising:

[0055] S1. By weight, 99 parts of commercial silicon powder and 1 part of yttrium oxide (Y2O3) powder are mixed evenly, and the mixed powder is subjected to high-energy refinement to obtain a silicon nitride reactant.

[0056] The high-energy ball milling adopts dry grinding process, uses carbide grinding balls for high-energy ball milling, the carbide grinding balls have a diameter of 10 mm, the ball-to-material mass ratio is 40:1, the ball milling rate is 200 rpm, the high-energy ball milling time is 12 h, and the ball milling is stopped for 5 min every 0.5 h during the high-energy ball milling process;

[0057] S2, subjecting the silicon nitride reactant obtained in step S1 to direct catalytic nitridation to obtain silicon nitride ceramic powder,

[0058] The specific conditions of direct catalytic nitridation treatment are: the reaction is carried out under a high-purity nitrogen flow atmosphere, the gas flow rate of the flowing atmosphere is 1.5L / min, the reaction temperature is 1580℃, the reaction time is 8h, and the furnace is cooled down after the reaction is completed;

[0059] Its purity is ≥99%.

[0060] Comparative Example 1

[0061] A method for preparing silicon nitride ceramic powder, the preparation method comprising:

[0062] S1. High-energy refinement of commercial silicon powder to obtain silicon nitride reactant.

[0063] The high-energy ball milling adopts dry grinding process, uses carbide grinding balls for high-energy ball milling, the carbide grinding balls have a diameter of 10 mm, the ball-to-material mass ratio is 40:1, the ball milling rate is 200 rpm, the high-energy ball milling time is 12 h, and the ball milling is stopped for 5 min every 0.5 h during the high-energy ball milling process;

[0064] S2, subjecting the silicon nitride reactant obtained in step S1 to direct catalytic nitridation to obtain silicon nitride ceramic powder,

[0065] The specific conditions of direct catalytic nitridation treatment are: reacting in a high-purity nitrogen flowing atmosphere, the gas flow rate of the flowing atmosphere is 1.5L / min, the reaction temperature is 1600°C, the reaction time is 8h, and the furnace is cooled down after the reaction is completed.

[0066] The silicon nitride ceramic powders prepared in Examples 1-11 were subjected to performance testing and purity analysis, wherein:

[0067] The average particle size of silicon nitride ceramic powder is detected by using a particle size analyzer combined with a scanning electron microscope;

[0068] The specific surface area detection method of silicon nitride ceramic powder is: specific surface instrument;

[0069] The purity of the silicon nitride ceramic powders prepared in Examples 1-11 is greater than or equal to 99%.

[0070] The above test results are shown in Table 1.

[0071] Table 1 Silicon nitride ceramic powder performance test table

[0072] serial number Rare Earth Oxides Rare earth oxide content (wt%) Average particle size (μm) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 <![CDATA[Y2O3]]> 1 1.13 3.11 Example 2 <![CDATA[Y2O3]]> 3 1.03 3.09 Example 3 <![CDATA[Y2O3]]> 5 1.06 3.06 Example 4 <![CDATA[Y2O3]]> 7 1.18 3.14 Example 5 <![CDATA[Y2O3]]> 10 1.14 3.21 Example 6 <![CDATA[La2O3]]> 1 1.21 3.25 Example 7 <![CDATA[Nd2O3]]> 1 1.34 3.24 Example 8 <![CDATA[Sm2O3]]> 1 1.07 3.15 Example 9 <![CDATA[Eu2O3]]> 1 1.11 3.07 Example 10 <![CDATA[Dy2O3]]> 1 1.09 3.22 Embodiment 11 <![CDATA[Er2O3]]> 1 1.32 3.16 Example 12 <![CDATA[Y2O3]]> 1 0.93 3.25 Comparative Example 1 / 0 1.65 2.26

[0073] As shown in Table 1, it can be seen that the method for preparing silicon nitride ceramic powder by using rare earth oxide as a catalyst to catalyze the nitridation of silicon powder is effective, and the catalytic nitridation effect of rare earth oxide on silicon powder is significant. Taking Examples 1-5 as examples, it can be seen that the content of rare earth oxide has an effect on the nitridation of silicon powder, which is mainly manifested in reducing the reaction temperature and reducing the grain size. It can be seen from Examples 1 and 6-11 that different rare earth oxides have similar effects on the nitridation of silicon powder, but yttrium oxide is preferred.

[0074] like Figure 1 As shown, it can be seen that after high-energy ball milling, the silicon powder has been fully refined, which is manifested by the broadening and weakening of the XRD diffraction peak, thereby improving the reaction efficiency.

[0075] In addition, as shown in the data of Example 12, the direct catalytic nitridation reaction temperature can be reduced by 20°C, the final powder particle size is reduced, the specific surface area is increased, but the phase purity is reduced. If no rare earth oxide is doped, the final powder particle size is significantly increased and the specific surface area is reduced.

[0076] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0077] The above is a detailed introduction to a silicon nitride ceramic powder and a preparation method thereof provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing silicon nitride ceramic powder, characterized in that: The method for preparing the silicon nitride ceramic powder comprises the following steps: S1. Mixing silicon powder and a catalyst and subjecting them to high-energy ball milling to obtain a silicon nitride reactant, wherein the catalyst is selected from one or more rare earth oxides, and the content of the catalyst in the silicon nitride reactant is 1-10 wt %; S2. Directly nitriding the silicon nitride reactant to obtain silicon nitride ceramic powder, wherein the reaction temperature of the direct nitridation reaction is 1300-1900°C.

2. The preparation method according to claim 1, characterized in that: The high-energy ball milling in step S1 is a dry milling process, using carbide grinding balls for ball milling. The carbide grinding balls have a diameter of 1-10 mm, a ball-to-material mass ratio of (40-20):1, a ball milling rate of 100-300 rpm, and a ball milling time of 2-24 h. During the ball milling process, the ball milling is stopped for 5-10 min every 0.5-1 h.

3. The preparation method according to claim 2, characterized in that: The cemented carbide grinding balls are tungsten carbide grinding balls with a diameter of 10 mm, a ball-to-material mass ratio of 40:1, a ball milling speed of 200 rpm, a ball milling time of 12 h, and the ball milling is stopped for 5 min every 0.5 h during the ball milling process.

4. The preparation method according to claim 1, characterized in that: The direct nitridation reaction in step S2 is carried out under a flowing atmosphere, wherein the flowing atmosphere is nitrogen and / or ammonia, and the gas flow rate of the flowing atmosphere is 0.5-2.5 L / min.

5. The preparation method according to claim 1, characterized in that: The reaction temperature of the direct nitridation reaction in step S2 is 1500-1600° C., and the reaction time is 4-24 hours.

6. The preparation method according to claim 1, characterized in that: The reaction temperature of the direct nitridation reaction in step S2 is 1580° C. and the reaction time is 8 h.

7. The preparation method according to claim 1, characterized in that: The catalyst in step S1 is selected from one or more of yttrium oxide, lanthanum oxide, neodymium oxide, samarium oxide, europium oxide, dysprosium oxide, and erbium oxide.

8. The preparation method according to claim 1, characterized in that: The catalyst is yttrium oxide.

9. The preparation method according to claim 1, characterized in that: The content of the catalyst in the silicon nitride reactant is 3-5%.

10. A silicon nitride ceramic powder prepared according to the preparation method according to any one of claims 1 to 9.

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