CN112552054A - Silicon nitride powder and water gas reduction preparation process thereof - Google Patents
Silicon nitride powder and water gas reduction preparation process thereof Download PDFInfo
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Abstract
The invention relates to silicon nitride powder and a water gas reduction preparation process thereof, wherein the silicon nitride ceramic powder is prepared from the following raw materials in parts by weight: 1.5-3% of calcium fluoride, 7-15% of sodium chloride, 22-40% of silicon powder, 4-6% of azodicarbonamide, 1.5-3% of dispersing agent, 1-4% of nano-scale fumed silica and 30-55% of solvent, wherein the sum of the weight percentages of the components is 100%. A preparation process of silicon nitride powder. According to the invention, silicon powder is used as a raw material, calcium fluoride and sodium chloride molten salt are used as diluents, azodicarbonamide is used as a foaming agent, the mixture is reduced under water gas and then is nitrided, and finally, the alpha-silicon nitride powder with small granularity and high purity is obtained.
Description
Technical Field
The invention relates to the field of materials, in particular to silicon nitride powder and a water gas reduction preparation process thereof.
Background
Silicon nitride powder is a high-temperature structural material with excellent performance, is generally applied to important fields of automobile industry, semiconductor industry and the like, but the large-scale production of the silicon nitride powder is restricted by an immature preparation process.
The direct silicon powder nitriding method is one of the main methods for producing silicon nitride powder in a large scale at present, has simple process and is suitable for large-scale production, but the direct silicon powder nitriding method is difficult to completely control the crystal phase of a product, generally can prepare micro powder with alpha and beta crystal phases mixed, and can often generate the phenomena of product adhesion or silicon overflow when the reaction temperature is higher, thereby influencing the continuous operation of the nitriding reaction. Meanwhile, because the silicon nitride product is agglomerated after the reaction is finished, the agglomerated product needs to be crushed to obtain fine powder, and the production cost is high. Therefore, in order to reduce the synthesis temperature of the silicon nitride powder and increase the alpha-phase silicon nitride content in the powder, the advantages of other preparation methods are absorbed, the problems in the existing production process are improved, and the production of high-quality silicon nitride powder is realized.
Disclosure of Invention
The invention provides silicon nitride powder and a water gas reduction preparation process thereof, which aim to overcome the defects in the prior art.
The invention adopts the following technical scheme:
the silicon nitride ceramic powder is prepared from the following raw materials in parts by weight: 1.5-3% of calcium fluoride, 7-15% of sodium chloride, 22-40% of silicon powder, 4-6% of azodicarbonamide, 1.5-3% of dispersing agent, 1-4% of nano-scale fumed silica and 30-55% of solvent, wherein the sum of the weight percentages of the components is 100%.
In a further improvement, the specification of the silicon powder is 325 to 1000 meshes, and the specification of the silicon powder is preferably 550 meshes.
In a further improvement, the specification of the nanoscale fumed silica is 15-25 nm, and preferably the specification of the nanoscale fumed silica is 20 nm.
In a further improvement, the dispersant is selected from one or more of polyvinyl alcohol, sodium dodecyl benzene sulfonate, maleic anhydride, methyl cellulose and polymethacrylate, and the preferable dispersant is polyvinyl alcohol, sodium dodecyl benzene sulfonate and polymethacrylate.
In a further improvement, the solvent is selected from one or more of benzene, toluene, xylene and solvent oil, and the preferred solvent is xylene and No. 100 solvent oil.
A water gas reduction preparation process of silicon nitride powder comprises the following steps:
step S1: mixing calcium fluoride, sodium chloride, silicon powder and azodicarbonamide in a certain proportion, ball-milling for 15-20 hours, adding a dispersing agent, nanoscale fumed silica and a solvent, uniformly mixing, spray-drying, sintering in an alumina atmosphere furnace, and reacting with water gas at 1000-1250 ℃ for 1-2 hours to obtain a silicon nitride prepolymer;
step S2: introducing nitrogen, reacting for 4-20 hours at 1300-1350 ℃, then soaking and cleaning with a mixed liquid of nitric acid and hydrofluoric acid, and finally washing with water for multiple times and drying in vacuum to obtain the a-silicon nitride powder with the purity of more than 98%.
In a further improvement, the volume ratio of the mixed liquid of nitric acid and hydrofluoric acid is (3-4): 1, and the preferred volume ratio of the mixed liquid of nitric acid and hydrofluoric acid is 3: 1.
As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages: the invention relates to silicon nitride powder, belonging to the field of ceramic materials, which is prepared by reducing silicon powder serving as a raw material, calcium fluoride and sodium chloride molten salt serving as diluents and azodicarbonamide serving as a foaming agent under the condition of water gas, and then nitriding to obtain alpha-silicon nitride powder with small granularity and high purity; the redox preparation process comprises the following steps: mixing calcium fluoride, sodium chloride, silicon powder and azodicarbonamide in a certain proportion, ball-milling for 15-20 hours, adding a dispersing agent, nanoscale fumed silica and a solvent, uniformly mixing, spray-drying, sintering in an alumina atmosphere furnace, and reacting with water gas at 1000-1250 ℃ for 1-2 hours to obtain a silicon nitride prepolymer; and introducing nitrogen, reacting for 4-20 hours at 1300-1350 ℃, soaking and cleaning by using a mixed solution of nitric acid and hydrofluoric acid, and finally washing with water for multiple times and drying in vacuum to obtain the alpha-silicon nitride powder with the purity of more than 98%. The silicon nitride powder prepared by the method has small granularity, high alpha-phase silicon nitride content, simple process, strong operability, cheap and easily available water gas, strong reducibility and low process cost, can realize low-temperature rapid nitridation, does not need cooling treatment in the middle, and solves the problems of high temperature and long time in the traditional method.
Detailed Description
The first implementation mode comprises the following steps:
the silicon nitride ceramic powder is prepared from the following raw materials in parts by weight: 2% of calcium fluoride, 11% of sodium chloride, 30% of silicon powder, 4% of azodicarbonamide, 2% of methyl cellulose, 2% of nano-grade gas-phase silicon dioxide and 50% of dimethylbenzene, wherein the sum of the weight percentages of the components is 100%. The specification of the silicon powder is 325-1000 meshes, and the specification of the preferred silicon powder is 550 meshes. The specification of the nanoscale fumed silica is 15-25 nm, and the specification of the nanoscale fumed silica is preferably 20 nm.
A preparation process of silicon nitride powder comprises the following steps:
step S1: 2g of calcium fluoride, 11g of sodium chloride, 30g of 500-mesh silicon powder and 3g of azodicarbonamide are subjected to dry mixing, after ball milling for 20 hours, 2g of dispersing agent, 2g of nanoscale fumed silica and 50g of xylene are added, the mixture is uniformly mixed, after spray drying, the mixture is sintered in an alumina atmosphere furnace, and after reaction with water gas at 1200 ℃ for 1 hour, a silicon nitride precursor is obtained;
step S2: introducing nitrogen, reacting for 10 hours at 1300 ℃, then soaking and cleaning by adopting mixed liquid of nitric acid and hydrofluoric acid (the volume ratio is 3: 1), finally washing by water for many times, and drying in vacuum to obtain the alpha-silicon nitride powder with the purity of 99%.
The volume ratio of the mixed liquid of the nitric acid and the hydrofluoric acid is (3-4) to 1.
The second embodiment:
the silicon nitride ceramic powder is prepared from the following raw materials in parts by weight: 3% of calcium fluoride, 15% of sodium chloride, 25% of silicon powder, 4% of azodicarbonamide, 1.5% of methyl cellulose, 2% of nano-grade fumed silica and 49.5% of xylene, wherein the sum of the weight percentages of the components is 100%.
Step S1: 3g of calcium fluoride, 15g of sodium chloride, 25g of silicon powder and 4g of azodicarbonamide are dry-mixed and ball-milled for 15 hours, then 1.5g of dispersing agent, 2g of nano-scale fumed silica and 49.5g of No. 100 solvent oil are added and uniformly mixed, after spray drying, the mixture is sintered in an alumina atmosphere furnace and reacts with water gas at 1000 ℃ for 1.5 hours to obtain a silicon nitride prepolymer;
step S2: introducing nitrogen, reacting for 15 hours at 1350 ℃, soaking and cleaning by using mixed liquid of nitric acid and hydrofluoric acid (the volume ratio is 3: 1), washing by water for multiple times, and drying in vacuum to obtain the alpha-silicon nitride powder with the purity of 98%.
The third embodiment is as follows:
the silicon nitride ceramic powder is prepared from the following raw materials in parts by weight: 2% of calcium fluoride, 11% of sodium chloride, 25% of silicon powder, 3% of azodicarbonamide, 3% of methyl cellulose, 4% of nano-grade gas-phase silicon dioxide and 52% of dimethylbenzene, wherein the sum of the weight percentages of the components is 100%.
Step S1: 2g of calcium fluoride, 11g of sodium chloride, 25g of silicon powder and 3g of azodicarbonamide are subjected to dry mixing and ball milling for 18 hours, then 3g of dispersing agent, nano 4g of meter-grade fumed silica and 52g of xylene are added, the mixture is uniformly mixed, and after spray drying, the mixture is sintered in an alumina atmosphere furnace and reacts with water gas at 1250 ℃ for 1 hour to obtain a silicon nitride precursor;
step S2: introducing nitrogen, reacting for 15 hours at 1300 ℃, then adopting mixed liquid of nitric acid and hydrofluoric acid (the volume ratio is 3: 1), soaking and cleaning, finally washing for many times, and drying in vacuum to obtain the alpha-silicon nitride powder with the purity of 99%.
The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.
Claims (7)
1. The silicon nitride ceramic powder is characterized by being prepared from the following raw materials in parts by weight: 1.5-3% of calcium fluoride, 7-15% of sodium chloride, 22-40% of silicon powder, 4-6% of azodicarbonamide, 1.5-3% of dispersing agent, 1-4% of nano-scale fumed silica and 30-55% of solvent.
2. The silicon nitride powder of claim 1, wherein: the specification of the silicon powder is 325-1000 meshes.
3. The silicon nitride powder of claim 1, wherein: the specification of the nanoscale fumed silica is 15-25 nm.
4. The silicon nitride powder of claim 1, wherein: the dispersing agent is selected from one or more of polyvinyl alcohol, sodium dodecyl benzene sulfonate, maleic anhydride, methyl cellulose and polymethacrylate.
5. The silicon nitride powder of claim 1, wherein: the solvent is selected from one or more of benzene, toluene, xylene and solvent oil.
6. The process for preparing silicon nitride powder according to any one of claims 1 to 5 by water gas reduction, wherein the process comprises the steps of:
step S1: (ii) a Mixing calcium fluoride, sodium chloride, silicon powder and azodicarbonamide in a certain proportion, ball-milling for 15-20 hours, adding a dispersing agent, nanoscale fumed silica and a solvent, uniformly mixing, spray-drying, sintering in an alumina atmosphere furnace, and reacting with water gas at 1000-1250 ℃ for 1-2 hours to obtain a silicon nitride prepolymer;
step S2: (ii) a Introducing nitrogen, reacting for 4-20 hours at 1300-1350 ℃, then soaking and cleaning with a mixed liquid of nitric acid and hydrofluoric acid, and finally washing with water for multiple times and drying in vacuum to obtain the a-silicon nitride powder with the purity of more than 98%.
7. The water gas reduction preparation process of silicon nitride powder according to claim 6, characterized in that: the volume ratio of the mixed liquid of the nitric acid and the hydrofluoric acid is (3-4) to 1.
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| CN105503198A (en) * | 2015-11-30 | 2016-04-20 | 衡阳凯新特种材料科技有限公司 | Silicon nitride material and preparation method thereof |
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| CN109608205A (en) * | 2019-02-02 | 2019-04-12 | 清华大学 | A method of the shaft-like α phase silicon nitride powder such as preparing |
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- 2021-01-13 CN CN202110044023.2A patent/CN112552054B/en active Active
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| US20090283307A1 (en) * | 2005-08-11 | 2009-11-19 | Denki Kagaku Kogyo Kabushiki Kaisha | Silicon nitride substrate, silicon nitride circuit substrate using the same, and its use |
| CN105503198A (en) * | 2015-11-30 | 2016-04-20 | 衡阳凯新特种材料科技有限公司 | Silicon nitride material and preparation method thereof |
| CN106810267A (en) * | 2017-02-21 | 2017-06-09 | 河北利福光电技术有限公司 | A kind of preparation method of high purity silicon nitride Si powder |
| CN109608205A (en) * | 2019-02-02 | 2019-04-12 | 清华大学 | A method of the shaft-like α phase silicon nitride powder such as preparing |
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