CN117800742B - Preparation method of alpha-phase silicon nitride powder - Google Patents
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- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 71
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 239000000843 powder Substances 0.000 title claims abstract description 56
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 71
- 239000011863 silicon-based powder Substances 0.000 claims abstract description 67
- 238000010438 heat treatment Methods 0.000 claims abstract description 58
- 239000007789 gas Substances 0.000 claims abstract description 39
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000011812 mixed powder Substances 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 31
- 238000002156 mixing Methods 0.000 claims abstract description 27
- 230000001681 protective effect Effects 0.000 claims abstract description 17
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 16
- 239000001257 hydrogen Substances 0.000 claims abstract description 14
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 14
- 238000011049 filling Methods 0.000 claims abstract description 13
- 238000010304 firing Methods 0.000 claims abstract description 13
- 102220043159 rs587780996 Human genes 0.000 claims abstract description 8
- 238000012216 screening Methods 0.000 claims abstract description 8
- 238000007873 sieving Methods 0.000 claims abstract description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 239000012467 final product Substances 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 49
- 239000003054 catalyst Substances 0.000 abstract description 4
- 239000000919 ceramic Substances 0.000 abstract description 4
- 239000012298 atmosphere Substances 0.000 abstract description 2
- 238000005265 energy consumption Methods 0.000 abstract description 2
- 239000002245 particle Substances 0.000 description 14
- 239000012071 phase Substances 0.000 description 14
- 239000003085 diluting agent Substances 0.000 description 12
- 238000005121 nitriding Methods 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- 239000010703 silicon Substances 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- 230000036632 reaction speed Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000005049 combustion synthesis Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- -1 electric power Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Abstract
The invention belongs to the technical field of ceramic powder preparation, and particularly relates to a preparation method of alpha-phase silicon nitride powder. The method comprises the following steps: (1) sieving: screening the silicon powder with the granularity D50=2-5 mu m to obtain six groups of silicon powder; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II; (2) batching: mixing the mixed powder I or the mixed powder II with silicon nitride powder to obtain a mixture; (3) charging: filling the mixture into a hearth, vacuumizing, and introducing protective gas; (4) firing: and (5) heating nitrogen or nitrogen-hydrogen mixed gas to perform firing under the atmosphere condition, thus obtaining the catalyst. The invention has low energy consumption, more complete reaction, easy control of the reaction process, good quality of the obtained powder and high content of alpha-phase silicon nitride.
Description
Technical Field
The invention belongs to the technical field of ceramic powder preparation, and particularly relates to a preparation method of alpha-phase silicon nitride powder.
Background
The silicon nitride ceramic has the excellent performances of high strength, high hardness, wear resistance, chemical corrosion resistance, self lubrication and the like. Can be used for manufacturing key parts of high-end equipment and is widely applied to the fields of steel, electric power, chemical industry, nonferrous metal smelting and casting, high-speed rail, aerospace, military and the like. The main raw material for manufacturing the silicon nitride ceramics is high alpha phase silicon nitride powder (the content of alpha phase silicon nitride is more than or equal to 93 percent). Silicon nitride powder does not exist in nature and must be synthesized artificially. The synthesis method of the silicon nitride powder mainly comprises gas phase synthesis, liquid phase synthesis and solid phase synthesis. The most commonly used method for synthesizing silicon nitride powder at present is to adopt a metal silicon powder nitriding process. The metal silicon powder is nitrided to synthesize silicon nitride powder by two methods, namely combustion synthesis, the process has high reaction speed and low cost, but is difficult to manufacture high alpha phase silicon nitride, but takes beta silicon nitride as the main material, and reaction synthesis, namely, the metal silicon powder is filled into a kiln, nitrogen is filled in, and the reaction is slow. Some of the reaction products can be completely reacted after about 20 days, and the reaction products have low efficiency and high cost.
The existing silicon nitride powder mainly adopts a direct nitriding method, namely silicon powder is subjected to chemical reaction in N 2,N2+H2 or NH 3 and other atmospheres at the temperature of 1200-1850 ℃ to generate the silicon nitride powder. The main advantage of this method is that the process flow is simpler, but there are still many problems in this method, such as how to control the reaction speed of metal silicon and nitrogen, how to ensure the nitriding rate of silicon powder, how to effectively use the heat released by metal silicon and nitrogen to avoid the "silicon flowing phenomenon" caused by local overheating, so a new method needs to be provided to solve these problems.
There are several patents reporting on the synthesis of silicon nitride powder, but there are also certain problems. For example, chinese patent application publication No. CN101983947a discloses a new method for synthesizing high-alpha phase silicon nitride powder by catalytic nitridation, in which FeCl 3•6H2 O is selected as a catalyst, si 3N4 is used as a diluent, and industrial Si powder is catalytically nitrided at 1350-1450 ℃ under the condition of nitrogen atmosphere, while silicon nitride powder with purity of 99.4% -99.8% and alpha phase silicon nitride content of 92% -95% is prepared, the catalyst is needed to increase the reaction speed, and the diluent Si 3N4 is needed to be added to slow down the reaction speed, so that the production cost is increased and the net yield of the product is reduced. The Chinese patent application publication No. CN101269803A discloses a preparation method of high alpha-Si 3N4 phase silicon nitride by controlling the temperature and nitrogen pressure: controlling the air pressure to be 5-30 kPa before 1000 ℃; the temperature is 1000-1200 ℃ and the air pressure is controlled at 10-30kPa; the pressure is controlled at 20-80 kPa at 1200-1350 ℃, so that silicon nitride powder with high a phase is obtained. However, since the silicon powder is continuous powder with granularity, the reaction temperature is continuous, and the silicon powder nitriding process is exothermic, the reaction is continuous, and the problems that the exothermic reaction is carried out along with the reaction, the reaction is faster and faster, and the control difficulty is increased are difficult to solve.
Disclosure of Invention
In order to solve the technical problems, the invention provides the preparation method of the alpha-phase silicon nitride powder, which has the advantages of low energy consumption, more sufficient reaction, easy control of the reaction process, good quality of the obtained powder and high content of the alpha-phase silicon nitride.
The preparation method of the alpha-phase silicon nitride powder comprises the following steps:
(1) And (3) screening: sieving silicon powder with the granularity D50=2-5 μm to obtain six groups of silicon powder with the granularity of less than 500nm, 500nm-1.5 μm, 1.5-5 μm, 5-10 μm, 10-40 μm and more than 40 μm respectively; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II;
(2) And (3) batching: mixing the mixed powder I or the mixed powder II with silicon nitride powder to obtain a mixture;
(3) And (2) charging: filling the mixture into a hearth, vacuumizing, and introducing protective gas;
(4) Firing: and (5) heating nitrogen or nitrogen-hydrogen mixed gas to perform firing under the atmosphere condition, thus obtaining the catalyst.
Preferably, in the step (3), the vacuum is applied to a degree of vacuum of (1-2). Times.10 -2 Pa.
Preferably, in the step (3), the shielding gas is nitrogen or a nitrogen-hydrogen mixed gas.
Preferably, in the step (3), a protective gas is introduced until the pressure reaches 0.1-0.15MPa.
Preferably, in the step (3), the mixture is firstly loaded into a sagger, then the sagger is loaded into a hearth, and the thickness of the mixture in the sagger is 3-10cm.
Preferably, the specific steps of the step (4) are as follows: the temperature rising rate of 3-5 ℃/min is increased from room temperature to air pressure, namely, the first-stage reaction is started, the temperature is T1, heating is stopped, the temperature is kept for 4-12 hours until nitrogen is not reacted, namely, the air pressure is not reduced; then heating to raise the temperature until the air pressure starts to decrease, namely starting the second-stage reaction, wherein the temperature is T2, stopping heating, and preserving the temperature for 4-12 hours until nitrogen is no longer reacted, namely the air pressure is no longer decreased; heating again until the air pressure starts to decrease, namely starting a third-stage reaction, wherein the temperature is T3, stopping heating, and preserving heat for 4-12 hours until nitrogen is no longer reacted, namely the air pressure is no longer decreased; and heating again until the air pressure starts to decrease, namely, the free silicon starts to react, wherein the temperature is T4, heating is stopped, and the temperature is kept for 4-12 hours until nitrogen is no longer reacted, namely, the air pressure is no longer decreased.
Preferably, t1=950-980 ℃, t2=1020-1100 ℃, t3=1140-1200 ℃, t4=1250-1300 ℃.
Preferably, in the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping the shielding gas during the firing process.
Preferably, the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed gas is 100:5.
Preferably, the purity of the nitrogen is more than or equal to 99 percent.
Preferably, the purity of the silicon powder and the silicon nitride powder is more than or equal to 99 percent.
Preferably, the silicon nitride powder is obtained by carrying out particle classification on raw material silicon nitride powder, and the particle size is 10-40 mu m.
Preferably, the mixed silicon powder I or the mixed silicon powder II accounts for 90% and the silicon nitride powder accounts for 10% in percentage by mass of the mixture.
According to the invention, silicon powder with continuous granularity is grouped according to the granularity range, then several groups with discontinuous granularity are taken for mixed reaction, and even if a certain group reacts, exothermic reaction is carried out, the non-adjacent group with larger granularity does not participate in the reaction, namely, the third group and the fifth group do not participate in the reaction in the first group of reaction, and the fifth group does not participate in the reaction in the third group of reaction; the silicon nitride generated during each group of reaction can be used as a diluent for the next group of reaction, meanwhile, silicon powder which does not participate in the reaction can also be used as a diluent, the amount of the diluent is more than or equal to 50 percent, the reaction heat release is controlled, the control of the reaction process is facilitated, and the energy is saved.
The nitriding reaction temperature of two groups of silicon powder with granularity less than 500nm and 500nm-1.5 mu m is 950-980 ℃; the nitriding reaction temperature of two groups of silicon powder with granularity of 1.5-5 mu m and 5-10 mu m is 1020-1100 ℃; the nitriding reaction temperature of two groups of silicon powder with the granularity of 10-40 mu m and more than 40 mu m is 1140-1200 ℃. To prevent the excessive high free silicon, the reaction process with the temperature of 1250-1300 ℃ is increased, and the heat is fully preserved.
The invention strictly controls the reaction temperature, when the mixed powder I is used for reaction, silicon powder with granularity less than 500nm, silicon powder with granularity of 1.5-5 mu m and silicon powder with granularity of 10-40 mu m are respectively reacted in the first section, the second section and the third section in sequence, and when the silicon powder with granularity less than 500nm is reacted, the silicon powder with granularity of 1.5-5 mu m and silicon powder with granularity of 10-40 mu m are not reacted, but are used as reaction diluents; after the first-stage reaction is finished, silicon nitride is obtained, and silicon powder with particle size of 10-40 mu m which does not participate in the reaction also becomes a diluent in the second-stage reaction; the silicon nitride obtained after the second-stage reaction and the silicon nitride obtained by the first-stage reaction also serve as diluents, so that the third-stage synthesis is facilitated.
Similarly, when the mixed powder II is used for reaction, silicon powder with the granularity of 500nm-1.5 mu m, silicon powder with the granularity of 5-10 mu m and silicon powder with the granularity of more than 40 mu m are reacted in the first section, the second section and the third section in sequence respectively, and when the silicon powder with the granularity of 500nm-1.5 mu m is reacted, the silicon powder with the granularity of 5-10 mu m and the silicon powder with the granularity of more than 40 mu m do not participate in the reaction, but are used as reaction diluents; after the first-stage reaction is finished, silicon nitride is obtained, and silicon powder with particle size more than 40 mu m which does not participate in the reaction also becomes a diluent in the second-stage reaction; the silicon nitride obtained after the second-stage reaction and the silicon nitride obtained by the first-stage reaction also serve as diluents, so that the third-stage synthesis is facilitated.
Compared with the prior art, the invention has the beneficial effects that:
1. in the existing silicon nitride preparation, a large amount of silicon nitride is needed to be added as a diluent, and the silicon nitride does not participate in the reaction but still consumes heat, so that the energy waste is caused;
2. the reaction process of the invention is discontinuous and controllable, the product quality is good, and the alpha-phase silicon nitride content in the powder is high.
Detailed Description
The technical scheme of the present invention will be clearly and completely described in the following examples.
All materials used in the examples are commercially available, except as specified.
Example 1
(1) And (3) screening: sieving silicon powder with purity of 99% and granularity D50=2μm to obtain six groups of silicon powder with granularity less than 500nm, 500nm-1.5 μm, 1.5-5 μm, 5-10 μm, 10-40 μm and more than 40 μm; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II;
(2) And (3) batching: mixing the mixed powder I with silicon nitride powder with the purity of 99%, and uniformly mixing to obtain a mixture; wherein, the silicon powder I is mixed by the mass fraction of the mixture: 90%, silicon nitride powder: 10%.
(3) And (2) charging: firstly, filling the mixture into a sagger, wherein the thickness of the mixture in the sagger is 10cm, then filling the sagger into a hearth, vacuumizing to a vacuum degree of 2X 10 -2 Pa, and introducing hydrogen with a purity of 99% as protective gas until the gas pressure is 0.1MPa;
(4) Firing: the temperature is increased from room temperature to air pressure at a heating rate of 3 ℃/min and is reduced, the temperature is 950 ℃, the heating is stopped, and the temperature is kept for 4 hours; then heating to raise the temperature until the air pressure starts to be reduced, wherein the temperature is 1020 ℃, and stopping heating and preserving heat for 4 hours; heating again until the air pressure starts to decrease, wherein the temperature is 1140 ℃, and stopping heating and preserving heat for 4 hours; and heating again until the air pressure starts to decrease, wherein the temperature is 1300 ℃, and stopping heating and preserving heat for 8 hours.
In the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping introducing the protective gas.
The silicon nitride powder is obtained by carrying out particle classification on raw material silicon nitride powder, and the particle size is 10-40 mu m.
Example 2
(1) And (3) screening: sieving silicon powder with purity of 99% and granularity D50=3μm to obtain six groups of silicon powder with granularity less than 500nm, 500nm-1.5 μm, 1.5-5 μm, 5-10 μm, 10-40 μm and more than 40 μm; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II;
(2) And (3) batching: mixing the mixed powder I with silicon nitride powder with the purity of 99%, and uniformly mixing to obtain a mixture; wherein, the silicon powder I is mixed by the mass fraction of the mixture: 90%, silicon nitride powder: 10%.
(3) And (2) charging: firstly, filling the mixture into a sagger, wherein the thickness of the mixture in the sagger is 3cm, then filling the sagger into a hearth, vacuumizing to a vacuum degree of 2X 10 -2 Pa, and introducing hydrogen with a purity of 99% as protective gas until the gas pressure is 0.1MPa;
(4) Firing: the temperature is increased from room temperature to air pressure at a heating rate of 5 ℃/min and is reduced, at the moment, the temperature is 960 ℃, the heating is stopped, and the temperature is kept for 6 hours; then heating to raise the temperature until the air pressure starts to be reduced, wherein the temperature is 1060 ℃, and stopping heating and preserving heat for 6 hours; heating again until the air pressure starts to decrease, wherein the temperature is 1150 ℃, and stopping heating and preserving heat for 6 hours; and heating again until the air pressure starts to decrease, wherein the temperature is 1290 ℃, and stopping heating and preserving heat for 6 hours.
In the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping introducing the protective gas.
The silicon nitride powder is obtained by carrying out particle classification on raw material silicon nitride powder, and the particle size is 10-40 mu m.
Example 3
(1) And (3) screening: sieving silicon powder with purity of 99% and granularity D50=5μm to obtain six groups of silicon powder with granularity less than 500nm, 500nm-1.5 μm, 1.5-5 μm, 5-10 μm, 10-40 μm and more than 40 μm; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II;
(2) And (3) batching: mixing the mixed powder I with silicon nitride powder with the purity of 99%, and uniformly mixing to obtain a mixture; wherein, the silicon powder I is mixed by the mass fraction of the mixture: 90%, silicon nitride powder: 10%.
(3) And (2) charging: firstly, filling the mixture into a sagger, wherein the thickness of the mixture in the sagger is 8cm, then filling the sagger into a hearth, vacuumizing to a vacuum degree of 1X 10 -2 Pa, and introducing hydrogen with a purity of 99% as protective gas until the gas pressure is 0.1MPa;
(4) Firing: the temperature is increased from room temperature to air pressure at a heating rate of 3 ℃/min and is reduced, the temperature is 980 ℃, the heating is stopped, and the temperature is kept for 8 hours; then heating to raise the temperature until the air pressure starts to be reduced, wherein the temperature is 1080 ℃, and stopping heating and preserving heat for 8 hours; heating again until the air pressure starts to decrease, wherein the temperature is 1180 ℃, and stopping heating and preserving heat for 8 hours; and heating again until the air pressure starts to decrease, wherein the temperature is 1280 ℃, and stopping heating and preserving heat for 8 hours.
In the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping introducing the protective gas.
The silicon nitride powder is obtained by carrying out particle classification on raw material silicon nitride powder, and the particle size is 10-40 mu m.
Example 4
(1) And (3) screening: sieving silicon powder with purity of 99% and granularity D50=2μm to obtain six groups of silicon powder with granularity less than 500nm, 500nm-1.5 μm, 1.5-5 μm, 5-10 μm, 10-40 μm and more than 40 μm; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II;
(2) And (3) batching: mixing the mixed powder II with silicon nitride powder with the purity of 99%, and uniformly mixing to obtain a mixture; wherein, the silicon powder II is mixed by the mass fraction of the mixture: 90%, silicon nitride powder: 10%.
(3) And (2) charging: firstly, filling the mixture into a sagger, wherein the thickness of the mixture in the sagger is 10cm, then filling the sagger into a hearth, vacuumizing to a vacuum degree of 2X 10 -2 Pa, and introducing nitrogen-hydrogen mixed gas with the volume ratio of nitrogen to hydrogen of 100:5 as protective gas until the gas pressure is 0.1MPa;
(4) Firing: the temperature is increased from room temperature to air pressure at a heating rate of 3 ℃/min and is reduced, at the moment, the temperature is 960 ℃, the heating is stopped, and the temperature is kept for 12 hours; then heating to raise the temperature until the air pressure starts to be reduced, wherein the temperature is 1060 ℃, and stopping heating and preserving heat for 12 hours; heating again until the air pressure starts to decrease, wherein the temperature is 1150 ℃, and stopping heating and preserving heat for 12 hours; and heating again until the air pressure starts to decrease, wherein the temperature is 1300 ℃, and stopping heating and preserving heat for 12 hours.
In the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping introducing the protective gas.
The silicon nitride powder is obtained by carrying out particle classification on raw material silicon nitride powder, and the particle size is 10-40 mu m.
Example 5
(1) And (3) screening: sieving silicon powder with purity of 99% and granularity D50=2.5 μm to obtain six groups of silicon powder with granularity less than 500nm, 500nm-1.5 μm, 1.5-5 μm, 5-10 μm, 10-40 μm and more than 40 μm; mixing three groups of silicon powder with granularity less than 500nm, 1.5-5 mu m and 10-40 mu m to obtain mixed powder I; mixing silicon powder with granularity of 500nm-1.5 μm, 5-10 μm and more than 40 μm to obtain mixed powder II;
(2) And (3) batching: mixing the mixed powder I with silicon nitride powder with the purity of 99%, and uniformly mixing to obtain a mixture; wherein, the silicon powder I is mixed by the mass fraction of the mixture: 90%, silicon nitride powder: 10%.
(3) And (2) charging: firstly, filling the mixture into a sagger, wherein the thickness of the mixture in the sagger is 10cm, then filling the sagger into a hearth, vacuumizing to a vacuum degree of 1X 10 -2 Pa, and introducing hydrogen with a purity of 99% as a protective gas
To a gas pressure of 0.1MPa;
(4) Firing: the temperature is increased from room temperature to air pressure at a heating rate of 3 ℃/min and is reduced, the temperature is 980 ℃, the heating is stopped, and the temperature is kept for 10 hours; then heating to raise the temperature until the air pressure starts to be reduced, wherein the temperature is 1100 ℃, and stopping heating and preserving heat for 10 hours; heating again until the air pressure starts to decrease, wherein the temperature is 1200 ℃, and stopping heating and preserving heat for 10 hours; and heating again until the air pressure starts to decrease, wherein the temperature is 1250 ℃, and stopping heating and preserving heat for 4 hours.
In the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping introducing the protective gas.
The silicon nitride powder is obtained by carrying out particle classification on raw material silicon nitride powder, and the particle size is 10-40 mu m.
Performance testing
The silicon nitride powders obtained in examples 1 to 5 were subjected to physical and chemical index tests, and the results are shown in Table 1. As can be seen from Table 1, the alpha-silicon nitride of the present invention has high content, low impurity content and good quality.
Table 1 examples 1-5 physical and chemical index test table
Claims (4)
1. The preparation method of the alpha-phase silicon nitride powder is characterized by comprising the following steps of:
(1) And (3) screening: sieving silicon powder with the granularity D50=2-5 μm to obtain six groups of silicon powder with the granularity of less than 500nm, granularity less than or equal to 500nm and less than 1.5 μm, granularity less than or equal to 1.5 μm and less than or equal to 5 μm, granularity less than or equal to 5 μm and less than or equal to 10 μm, granularity less than or equal to 10 μm and less than or equal to 40 μm and more than 40 μm respectively; three groups of silicon powder with granularity less than 500nm, granularity less than or equal to 1.5 mu m and less than or equal to 5 mu m and granularity less than or equal to 10 mu m and less than or equal to 40 mu m are mixed to be used as mixed powder I; silicon powder with the granularity of less than or equal to 500nm and less than 1.5 mu m, the granularity of less than or equal to 5 mu m and less than 10 mu m and the granularity of more than 40 mu m is mixed to be used as mixed powder II;
(2) And (3) batching: mixing the mixed powder I or the mixed powder II with silicon nitride powder to obtain a mixture;
(3) And (2) charging: filling the mixture into a hearth, vacuumizing, and introducing protective gas;
(4) Firing: heating and firing to obtain the final product;
The specific steps of the step (4) are as follows: the temperature is increased from room temperature to air pressure at a heating rate of 3-5 ℃/min and is reduced, the temperature is T1, heating is stopped, and the temperature is kept for 4-12h; then heating to raise the temperature until the air pressure starts to be reduced, wherein the temperature is T2, stopping heating, and preserving the heat for 4-12h; heating again until the air pressure starts to decrease, wherein the temperature is T3, stopping heating, and preserving heat for 4-12h; heating again until the air pressure starts to decrease, wherein the temperature is T4, stopping heating, and preserving heat for 4-12h;
T1=950-980℃，T2=1020-1100℃，T3=1140-1200℃，T4=1250-1300℃；
In the step (3), the protective gas is nitrogen or nitrogen-hydrogen mixed gas;
in the step (3), protective gas is introduced until the pressure reaches 0.1-0.15MPa;
in the step (4), the gas pressure is always maintained at 0.1-0.15MPa by introducing/stopping introducing protective gas in the firing process;
the mass fraction of the mixed powder I or the mixed powder II is 90%, and the silicon nitride powder is 10%.
2. The method for producing alpha-phase silicon nitride powder according to claim 1, wherein in step (3), the vacuum is applied to a degree of vacuum of (1-2). Times.10 -2 Pa.
3. A method for producing alpha-phase silicon nitride powder according to claim 1, wherein the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed gas is 100:5.
4. The method for producing alpha-phase silicon nitride powder according to claim 1, wherein in step (3), the mixture is charged into a sagger first, and then the sagger is charged into a hearth, and the thickness of the mixture in the sagger is 3 to 10cm.
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| EP0186497A2 (en) * | 1984-12-28 | 1986-07-02 | Onoda Cement Company, Ltd. | Process for producing silicon nitride of high alpha content |
| CN102173397A (en) * | 2011-01-25 | 2011-09-07 | 巩义市宏泰氮化硅材料有限公司 | Production method of high-content silicon nitride (Si3N4) powder |
| CN104291829A (en) * | 2014-04-30 | 2015-01-21 | 浙江大学 | Preparation method for high alpha-phase silicon nitride |
| CN107759238A (en) * | 2017-10-27 | 2018-03-06 | 中钢宁夏耐研滨河新材料有限公司 | The Nitride firing method of silicon nitride combined silicon carbide refractory product |
| CN115072678A (en) * | 2022-08-22 | 2022-09-20 | 河北正雍新材料科技有限公司 | Preparation method of silicon nitride |
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| EP0186497A2 (en) * | 1984-12-28 | 1986-07-02 | Onoda Cement Company, Ltd. | Process for producing silicon nitride of high alpha content |
| CN102173397A (en) * | 2011-01-25 | 2011-09-07 | 巩义市宏泰氮化硅材料有限公司 | Production method of high-content silicon nitride (Si3N4) powder |
| CN104291829A (en) * | 2014-04-30 | 2015-01-21 | 浙江大学 | Preparation method for high alpha-phase silicon nitride |
| CN107759238A (en) * | 2017-10-27 | 2018-03-06 | 中钢宁夏耐研滨河新材料有限公司 | The Nitride firing method of silicon nitride combined silicon carbide refractory product |
| CN115072678A (en) * | 2022-08-22 | 2022-09-20 | 河北正雍新材料科技有限公司 | Preparation method of silicon nitride |
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