CN1286713C - Method for synthesizing silicon nitride powder by normal pressure combustion - Google Patents
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- CN1286713C CN1286713C CN 200410039170 CN200410039170A CN1286713C CN 1286713 C CN1286713 C CN 1286713C CN 200410039170 CN200410039170 CN 200410039170 CN 200410039170 A CN200410039170 A CN 200410039170A CN 1286713 C CN1286713 C CN 1286713C
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- 239000000843 powder Substances 0.000 title claims abstract description 80
- 238000000034 method Methods 0.000 title claims abstract description 52
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 50
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 238000002485 combustion reaction Methods 0.000 title abstract description 21
- 230000002194 synthesizing effect Effects 0.000 title abstract description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 61
- 238000006243 chemical reaction Methods 0.000 claims abstract description 48
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 31
- 238000005049 combustion synthesis Methods 0.000 claims abstract description 26
- 239000011863 silicon-based powder Substances 0.000 claims abstract description 26
- 238000001994 activation Methods 0.000 claims abstract description 22
- 230000004913 activation Effects 0.000 claims abstract description 20
- 239000003054 catalyst Substances 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims description 26
- 230000008569 process Effects 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 13
- 238000004137 mechanical activation Methods 0.000 claims description 13
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 7
- 229910021529 ammonia Inorganic materials 0.000 claims description 6
- 235000008331 Pinus X rigitaeda Nutrition 0.000 claims description 5
- 235000011613 Pinus brutia Nutrition 0.000 claims description 5
- 241000018646 Pinus brutia Species 0.000 claims description 5
- 150000003863 ammonium salts Chemical class 0.000 claims description 5
- 238000000498 ball milling Methods 0.000 claims description 5
- 239000000654 additive Substances 0.000 claims description 4
- 230000000996 additive effect Effects 0.000 claims description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 239000010937 tungsten Substances 0.000 claims description 4
- -1 nitrogen-containing compound Chemical class 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims 1
- 238000003756 stirring Methods 0.000 claims 1
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- 238000000227 grinding Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 4
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- 241000196324 Embryophyta Species 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention belongs to the technical field of preparation of non-oxide superfine silicon nitride ceramic powder, and relates to a method for synthesizing silicon nitride powder by normal pressure combustion, in particular to a method for preparing silicon nitride powder by normal pressure combustionRelates to a method for synthesizing silicon nitride powder by normal pressure continuous combustion. The method comprises the steps of mixing Si powder and a catalyst according to the weight ratio of Si to the catalyst of 94-40: 3-30, adding silicon nitride for powder activation treatment, and inducing combustion synthesis reaction under the conditions of normal temperature and normal pressure. The invention is characterized in that a high-pressure reaction device is not needed, and the reaction can be carried out in a nitrogen atmosphere with micro-positive pressure or flowing nitrogen or air by only loosely placing the powder in a high-temperature resistant porous reactor. The activation treatment of the powder is beneficial to adjusting the reaction temperature, and the main substance in the synthesized product is Si3N4The main crystal phase is alpha-Si accounting for 85-95% of the total weight3N4And (3) pulverizing. The invention has the advantages of short production period, energy saving and less equipment investment.
Description
Technical field
The invention belongs to non-oxidized substance superfine silicon nitride Technique for Preparing Ceramic Powders field, relate to the method for normal pressure combustion synthesis of silicon nitride powder, particularly the method for normal pressure serialization burning synthesizing silicon nitride powder.
Background technology
Si
3N
4Pottery is the important representative of non-oxide ceramic material, because its excellent high strength, high rigidity, wearability and resist chemical performance are widely used in the aspects such as ceramic tip, bearing, wire drawing die, roll.But for metal_based material, the cost that silicon nitride ceramics is high has restricted its scale and has used.Therefore, researching and developing new low price technology of preparing from powder process-moulding-sintering-processing four processes is study hotspot in the international coverage.
The Si that researchs and develops in the world
3N
4Powder preparation method is a lot, and representational method is the SiO of U.S. Dow Chemical Co. exploitation
2The carbothermal reduction-nitridation method, and the silica flour direct nitridation method that generally adopts in the world.There are factories such as Starck (moral), AME (English), Kemanord (Sweden) and Japanese electrician in big in the world manufacturer.But two kinds of processing methodes all need very long nitridation time, and prepared alpha-silicon nitride powders price is also higher.The silicon powder nitride legal system of U.S.'s report is got Si
3N
4Price be 35 dollars/kilogram.And the actual average price of the beta-silicon nitride powder of world market is about 45 dollars/kilogram.Owing to the powder characteristic reason, the generally accepted powder in world market is still the product (adopt ammonolysis process on the processing method, product price is 120 dollars/kilogram) of Japanese Ube company, and is all the more so when especially preparing ceramic gas turbine with parts.In recent years, the plasma method of the preparation nano-silicon nitride powder of domestic many units exploitation is not because product price and production scale still possess the possibility that forms big industry.
Combustion synthesis technology (Combustion Synthesis, abbreviation CS) is the new technology of the synthesized high-performance material of USSR (Union of Soviet Socialist Republics) scientist invention.Burning is synthetic also to claim self propagating high temperature to synthesize (Self-propagating High-temperature Synthesis, abbreviation SHS), with regard to its process characteristics, be meant that the chemical reaction system to high heat release provides certain energy to bring out its local exothermic chemical reaction (be called and light) that takes place by the external world, form combustion reactions forward position (being called combustion wave), utilize reaction self liberated heat to make combustion wave constantly spontaneous expansion (spreading certainly) forward in reactant then, all change product into until reactant, thereby synthesize the process of needed material in a short period of time.Promptly lighting → form combustion wave → combustion wave in brief spreads → and be product with the reactant fast transition.Outstanding advantage when above characteristics have determined that combustion synthesis process is used for synthesizing silicon nitride is:
(1) be swift in response: it is with short production cycle generally to finish building-up reactions (traditional silica flour direct nitridation method needs 72 hours) in 30 minutes～1 hour;
(2) power consumption is low: except that the energy that starts the required minute quantity of reaction, material is synthetic to be undertaken by the id reaction liberated heat, does not need importing into of outside heat;
(3) self-purification: because in synthetic reaction process, the effusion of volatilizing of the detrimental impurity in the raw material is so product purity is easy to raising;
(4) equipment and technology are simple, investment is little, equipment interoperability is strong: be suitable for preparing other all kinds of inorganic materials, as all kinds of potteries (AlN, TiCN, Mg
2NiH
4Deng), ceramic composite and intermetallic compound etc.;
(5) the sintering activity height of powder: in combustion process, because material has experienced very big thermograde, product exists defective and the non-equilibrium phase of high concentration, synthetic α-Si
3N
4The sintering activity height of powder.
Preparing with combustion synthesis technology aspect the silicon nitride powder material, from nineteen ninety-five so far, the existing a large amount of patents of various countries scholar and research paper report.These results respectively have pluses and minuses: " a kind ofly prepare high α-Si such as inventions such as Russian Merzhanov
3N
4Method " (US Patent No. 5032370); need to be under higher nitrogen pressure (4～30MPa) finish synthetic reaction; especially need to add the ammonium salt that contains in a large number Cl, F; addition is up to 50%; the HCl, the HF gas that produce after the reaction are serious to equipment corrosion; accelerated equipment depreciation, improved the maintenance costs such as detection, flaw detection.There is above shortcoming equally in " preparation method of self propagating high temperature synthesizing silicon nitride iron powder " (the Chinese patent publication number is CN1275526) of the inventions such as Jiang Guojian of Chinese Shanghai silicate institute, and owing to adopt ferrosilicon powder to make raw material, product ferrous contaminants height, can not make product reach of the requirement of ceramic grade product even increase pickling process to raw material, and can only be as being worth lower refractory materials.Single heat static reaction at above two kinds of methods, can not serialization synthetic shortcoming, the Chen Ke of Tsing-Hua University newly waits the people to invent " method of the synthetic alpha-phase silicon nitride powder of a kind of low-pressure combustion " (the Chinese patent publication number is CN1362358A), realized that serialization suspension nitrogenize synthesizes beta-silicon nitride powder, but this method is when improving productive rate, but bring the plant issue such as complicated of ignition system, gathering system, made equipment manufacturing cost improve.
For the characteristics that the low price of giving full play to gas-solid system combustion synthesis technology prepares, two aspects are devoted in domestic and international research work always: the one, realize that the normal pressure burning is synthetic, and the 2nd, realize that serialization prepares.Could realize scale on this basis, thereby reduce production costs.To the synthetic Si that burns
3N
4Research undertaken by this thinking just: 1987, the Munir professor of California, USA university write articles at J.Mater.Sci. and points out, theoretical calculating showing the synthetic Si of burning
3N
4Be higher than 10
4Could realize under the nitrogen pressure of Mpa.But professor Miyamoto of Osaka, Japan university in 1988 adds the process of nucleating agent has realized the synthetic Si of burning under the 10Mpa nitrogen pressure
3N
4The Shanghai silicate research institute of the state university in USA New York (1992) and China and University of Science ﹠ Technology, Beijing (1993) have in succession reported and realized the synthetic Si of burning under 3Mpa pressure subsequently
3N
4At the synthetic Si of burning
3N
4The aspect, the patent of Russian nineteen ninety-five has represented the highest level of high pressure list heat mode synthetic technology, the Si that they synthesize
3N
4α-Si in the powder
3N
4Content is up to more than 95%, thereby has good sintering character.No matter but be research or industrialization, Si is synthesized in up to now domestic and international all burnings
3N
4Work all is to carry out under far above the nitrogen pressure of 3Mpa, thereby can not realize serialization and then large-scale production.Therefore, the method for exploitation normal pressure serialization Combustion Synthesis of Si_3 N_4 ceramic powders seems very necessary.
Summary of the invention
One of purpose of the present invention is: carry out in the high pressure specific equipment at synthetic requirement of high-pressure combustion, and equipment cost is higher, the shortcoming of poor stability, a kind of method of the synthesizing silicon nitride powder that burns under normal pressure is provided.
Two of purpose of the present invention is in line with the principle for preparing silicon nitride ceramic powder at a low price, at the shortcoming that the high-pressure combustion synthesis technique can only be single heat production, productive rate is low, provide a kind of method that can in the nitrogen of pressure-fired nitrogen, atmospheric flow or air, carry out normal pressure serialization combustion synthesis of silicon nitride powder.
The present invention is Si by weight by Si powder and catalyst: catalyst=94～40: 3～30 ratio is mixed, and adds then Si
3N
4Carry out the powder activation process, subsequently inducing combustion synthetic reaction under normal temperature and pressure conditions.Characteristics of the present invention are not need high pressure reaction assembly, only need the powder pine is loaded in the resistant to elevated temperatures perforated reactor, and reaction can be carried out in the blanket of nitrogen of pressure-fired or flowing nitrogen or air.The powder activation process is conducive to adjust reaction temperature, and main matter is Si in the synthetic product
3N
4, principal crystalline phase is the α-Si that accounts for gross weight 85～95%
3N
4Powder, color are canescence.
The method of normal pressure combustion synthesis of silicon nitride powder of the present invention may further comprise the steps:
(1). raw material mixes and activation treatment:
Press pure silicon powder: Si
3N
4: catalyst=94～40: 60～8: 3～30 weight portion ratio is with pure silicon powder, Si
3N
4Fully mix with catalyst, mixed material is processed through high energy mechanical activation process or ultrasonic activation; Or press pure silicon powder: Si
3N
4=94～40: 60～8 weight portion ratio is with pure silicon powder and Si
3N
4Fully mix, more mixed material powder is processed through high energy mechanical activation process or ultrasonic activation in ammonia, with formation reaction is had the middle phase of amorphous of catalytic effect, thereby carry the activity of high-purity silicon powder reactant, the reactant powder after obtaining activating; It is standard that the active amorphous content of determining by the quantitative result of calculation of means of differential scanning calorimetry/thermogravimetric (DSC/TG) analysis of reactant is no less than 5wt%.
(2). the burning nitrogenizing reaction:
The mixed material pine of step (1) through high energy mechanical activation process or ultrasonic activation processing is loaded in the resistant to elevated temperatures container (such as the porous graphite crucible), and apparent density is 1.0～2.4g/cm
3Then container is put into suitable reactor (as vacuum glove box), under nitrogen atmosphere, flowing nitrogen or the air conditions of pressure-fired, bring out powder systems generation combustion synthesis reaction with the local heating mode, the material after the naturally cooling burning is synthetic obtains beta-silicon nitride powder.
(3). the crystallization phase inversion is handled:
Press the difference of temperature of reaction system, can obtain amorphous phase Si
3N
4, α-Si
3N
4, β-Si
3N
4Or its mixture.Usually, when maximum combustion temperature was lower than 1600 ℃, product was with α-Si
3N
4Be main; When maximum combustion temperature was higher than 1600 ℃, product was with β-Si
3N
4Be main; In the synthetic product in two kinds of situations amorphous phase Si is arranged generally
3N
4For the amorphous phase silicon nitride in the product, can in flowing nitrogen, carry out in short-term heat treatment at 1350 ℃～1650 ℃, to change the α-Si of crystalline phase into
3N
4Or β-Si
3N
4Or its mixture.
Or
(1). raw material mixes and activation treatment:
Press pure silicon powder: Si
3N
4: catalyst=94～40: 60～8: 3～30 weight portion ratio is with pure silicon powder, Si
3N
4After fully mixing with catalyst, mixed material is processed through high energy mechanical activation process or ultrasonic activation; Or press pure silicon powder: Si
3N
4=94～40: 60～8 weight portion ratio is with pure silicon powder and Si
3N
4Fully mix, more mixed material powder is processed to form the middle phase of amorphous that reaction is had catalytic effect through high energy mechanical activation process or ultrasonic activation in ammonia, thereby improve the activity of reactant Si powder, the reactant powder after obtaining activating; It is standard that the active amorphous content of determining by the quantitative result of calculation of means of differential scanning calorimetry/thermogravimetric (DSC/TG) analysis of reactant is no less than 5wt%.
(2). serialization burning nitrogenizing reaction:
The mixed material pine of step (1) through high energy mechanical activation process or ultrasonic activation processing is loaded in the resistant to elevated temperatures container (such as the porous graphite crucible), and apparent density is 1.0～2.4g/cm
3Then container is put into suitable reactor (as vacuum glove box), under nitrogen atmosphere, flowing nitrogen or the air conditions of pressure-fired, after employing is brought out powder systems generation heat-producing chemical reaction with the local heating mode of reaction system, again to reaction system top continuous feeding, mode in the continuous discharging of reactor bottom realizes serialization burning synthetic (seeing accompanying drawing 1A) simultaneously, obtains beta-silicon nitride powder;
Or the mixed material that step (1) is processed through high energy mechanical activation process or ultrasonic activation with the high-temperature field of fluidization mode by the suspension calcining stove, is realized serialization burning synthetic (seeing accompanying drawing 1B) take high pure nitrogen or general nitrogen as carrier gas; Material after the burning that obtains is synthetic adopts naturally cooling in flowing nitrogen or air, obtains beta-silicon nitride powder.
(3). the crystallization phase inversion is handled:
Press the difference of temperature of reaction system, can obtain amorphous phase Si
3N
4, α-Si
3N
4, β-Si
3N
4Or its mixture.Usually, when serialization burning nitridation reaction maximum combustion temperature was lower than 1600 ℃, product was with α-Si
3N
4Be main; When maximum combustion temperature was higher than 1600 ℃, product was with β-Si
3N
4Be main; In the synthetic product in two kinds of situations amorphous phase Si is arranged
3N
4To with product in the amorphous phase silicon nitride, can in flowing nitrogen, carry out in short-term heat treatment at 1350～1650 ℃, to change the α-Si of crystalline phase into
3N
4Or β-Si
3N
4Or its mixture.
Described high energy mechanical activation treatment is meant that material grinds refinement and decrystallized in equipment such as high-energy planetary formula ball mill, the horizontal rotor shredder of high energy, high energy vibrations shredder or agitating ball mill.Activation degree is no less than 5wt% with amorphous content and is advisable.
Described bring out the mode of powder systems generation combustion synthesis reaction or bring out powder systems generation heat-producing chemical reaction comprise and adopt microwave heating, electrical spark heating, make mode that heating element feeds 10～30 amperes electric current with tungsten helix or carbon paper and heat and realize.
Described reactor is vacuum glove box, sealable steel construction retort or unlimited tube furnace etc., as long as can guarantee the reaction atmosphere of relative rich nitrogen.
Described reactor also can be suspension calcining stove or eddy flow dynamic calcining stove.
Described catalyst can adopt ammonium salt or CO (NH
2)
2The nitrogen-containing compound additive.
Described ammonium salt additive can be selected from NH
4F, (NH
4)
2CO
3, NH
4The mixture of one or more among the Cl, when being selected from two or more mixed catalyst, the ratio between them such as is at a weight ratio; Add-on is 3～30wt% of raw material total amount.Catalyzer also can adopt ammonia, does to grind protective atmosphere with ammonia, can play katalysis equally, just the reagent powder is ground in ammonia atmosphere, forms Si-NH by grinding
3Give reaction intermediate, the nitrogenize combustion synthesis reaction that catalysis is follow-up.
According to method operation of the present invention, after heat-producing chemical reaction is brought out in the part of reactant powder systems, can carry out continuously feed from top to reaction system, synthesize (seeing signal Figure 1A) from the bottom continuous discharge to realize the serialization burning simultaneously; Also can with reactant powder nitrogen buffer gas, realize serialization burning synthetic (seeing signal Figure 1B) in the fluidization mode through the suspension calcining stove.
Normal pressure burning synthesis method of the present invention, especially serialization burning synthesis method utilize Si-N on the one hand as far as possible fully
2Exothermic heat of reaction, utilize activating technology to improve the reagent activity on the other hand, reduced reaction activity, simultaneously owing to adopt the reagent continuously feeding mode shown in Figure 1A or to make reagent pass through reaction zone continuously with nitrogen do carrier gas shown in Figure 1B in the fluidization mode, therefore, must have more the advantage energy-conservation, that productive rate is high.And all systems with thermopositive reaction feature had general suitability.This method is particularly suitable for the infiltration burning of gas-solid phase system and synthesizes.
The method of normal pressure combustion synthesis of silicon nitride powder of the present invention has following advantage:
1. by adding catalyzer and reagent Si powder being carried out the high energy mechanical activation treatment, improved the reactive behavior of reagent, reduced the intensity of activation of combustion synthesis reaction, make building-up reactions in the rich nitrogen atmosphere of normal pressure, be achieved, solved the dependency of burning synthesizing silicon nitride technology to special high-pressure equipment, improve production security, reduced production cost.
2. combustion synthesis of silicon nitride powder carries out at normal pressure, the synthesis device cost is low, make the single heat production of burning synthesizing silicon nitride from the high-pressure combustion synthesis technique change into serialization production, improved product production, reduce cost, more can give full play to the advantage of the low price preparation of combustion synthesis technology than the high-pressure combustion synthetic method.
Description of drawings
Figure 1A: the reaction unit synoptic diagram of realizing normal pressure serialization combustion synthesis of silicon nitride powder from the bottom continuous discharge;
Figure 1B: the reaction unit synoptic diagram of realizing normal pressure serialization combustion synthesis of silicon nitride powder in the fluidization mode through the suspension calcining stove;
Fig. 2: the X-ray diffracting spectrum of normal pressure serialization combustion synthesis of silicon nitride powder;
Fig. 3: the electron scanning micrograph of normal pressure serialization combustion synthesis of silicon nitride powder.
Embodiment
Embodiment 1:
With the Si powder of average grain diameter 0.1 μ m and the Si of average grain diameter 0.5 μ m
3N
4Powder, by weight the Si powder be 55%, Si
3N
424%, NH
4F 21% put into the planetary ball mill ball milling 150 hours after mixing, and it is fully mixed and activates, and ball grinder is put into vacuum glove box, after vacuumizing, was filled with high pure nitrogen, until nitrogen pressure reaches 0.11Mpa; Take out mixed half material and place the porous graphite crucible in vacuum glove box, the apparent density that makes powder is 0.95～1.59g/cm
3Tungsten filament with diameter 0.5mm is made heating element, feeds 13 amperes electric current, and the material powder burning is brought out in igniting, combustion reactions continued after 10 minutes, and second half compound is added to the top of porous graphite vessels crucible, treat that whole example reactions finish after, sample is cooled to room temperature, again with N
2Emit, the fine grinding product, can obtain α phase silicon nitride content is the beta-silicon nitride powder of 84Wt%, wherein the content of remaining Si is 11%.Through the DSC/TG analysis revealed: the amorphous content in the reagent powder after milled processed is 25wt%.
Embodiment 2
With the Si powder of average grain diameter 0.5 μ m and the Si of average grain diameter 78 μ m
3N
4Powder, by weight the Si powder be 75%, Si
3N
4After 25% mixing, put into the ball grinder that can fill protection gas, be filled with NH
3Gas, ball milling is 120 hours in vibrator, and it is fully mixed, and draws through the DSC/TG analytical calculation that amorphous content is 21wt% in the mixture.Mixed material is placed in the porous graphite crucible, and the maintenance loose density is 0.95～1.59g/cm
3, put into the gas pressure sintering stove; After vacuumizing, charge into high pure nitrogen, reach 0.12Mpa up to nitrogen pressure; Make heating element with diameter less than the tungsten filament of 0.5mm, feed 16 amperes electric current, the material powder burning is brought out in igniting, combustion reactions continued after 25 minutes, emptying gas, fine grinding product, can obtain α phase silicon nitride content and be 70% beta-silicon nitride powder, the X-ray diffraction analysis does not have free Si.
Embodiment 3
The Si powder of average grain diameter 5 μ m and the Si of average grain diameter 30nm
3N
4Powder, by weight the Si powder be 50%, Si
3N
412% mixes, and puts into baking oven under 100 ℃ of conditions dry 1.5 hours, adds (NH after taking out
4)
2CO
319%, NH
4Cl 19%, processes through 30 minutes ultrasonic activations again, puts into then the planetary ball mill ball milling 120 hours, is filled with High Purity Nitrogen protection gas in the ball grinder, makes it fully mix refinement, and drawing amorphous content through the DSC/TG analytical calculation is 30wt%.Mixed material pine is installed in the porous ceramics cup, and the maintenance apparent density is 0.95～1.59g/cm
3, the porous ceramics cup is put into the civilian micro-wave oven of repacking; Be filled with high pure nitrogen from the bottom, with the nitrogen that flows as protection gas; Start microwave source, heat and can bring out material powder after 1 minute and burn, combustion reaction finishes after about 15 minutes, and the fine grinding product can obtain α phase silicon nitride content and be 93% beta-silicon nitride powder, and the X-ray diffraction analysis does not have free Si.The X-ray diffraction of this product is analyzed collection of illustrative plates and is seen accompanying drawing 2, and its microscopic appearance photo is seen accompanying drawing 3.
Embodiment 4
The Si powder of average grain diameter 5 μ m and the Si of average grain diameter 30nm
3N
4Powder, by weight the Si powder be 50%, Si
3N
412% mixes, and puts into baking oven under 100 ℃ of conditions dry 1.5 hours, adds (NH after taking out
4)
2CO
319%, NH
4Cl 19%, processes through 30 minutes ultrasonic activations again, puts into vibrations ball mill ball milling 120 hours, is filled with High Purity Nitrogen protection gas in the ball grinder, makes it fully mix refinement, draws through the DSC/TG analytical calculation that amorphous content is 33wt% in the mixed-powder.。Mixed material is blown into (synoptic diagram is seen accompanying drawing 1B) the suspension calcining stove from the bottom, the carrier gas that blows powder is a high pure nitrogen, and carrier gas also is a reactant gases simultaneously.The flow velocity of the boiler tube of flowing through of carrier gas and material is about 4～6m/s.Heating is brought out material powder incendiary temperature and is not less than 1200 ℃, and combustion reactions is finished behind the boiler tube by the suspension calcining stove continuously substantially at powder.The fine grinding product can obtain α phase silicon nitride content and be 93% beta-silicon nitride powder, and the X-ray diffraction analysis does not have free Si.As long as continuous feeding can be realized the serialization combustion synthesis of silicon nitride powder, this Nitrogen During atmospheric pressure is pressure-fired (namely a little more than 1atm).
Claims (5)
1. the method for a normal pressure combustion synthesis of silicon nitride powder, it is characterized in that: described method may further comprise the steps:
(1). raw material mixes and activation treatment:
Press pure silicon powder: Si
3N
4: catalyst=94～40: 60～8: 3～30 weight portion ratio is with pure silicon powder, Si
3N
4Fully mix with catalyst, mixed material is processed through high energy mechanical activation process or ultrasonic activation;
Or press pure silicon powder: Si
3N
4=94～40: 60～8 weight portion ratio is with pure silicon powder and Si
3N
4Fully mix, mixed material powder is processed through high energy mechanical activation process or ultrasonic activation in ammonia;
(2). serialization burning nitrogenizing reaction:
The mixed material pine of step (1) through high energy mechanical activation process or ultrasonic activation processing is loaded in the resistant to elevated temperatures container, and apparent density is 1.0～2.4g/cm
3Then container is put into reactor, under blanket of nitrogen, flowing nitrogen or the air conditions of pressure-fired, after employing is brought out powder systems generation heat-producing chemical reaction with the local heat mode of reaction system, again to reaction system top continuous feeding, mode at the reactor bottom continuous discharge realizes that the serialization burning is synthetic simultaneously, obtains beta-silicon nitride powder;
Described catalyst adopts ammonium salt or CO (NH
2)
2The nitrogen-containing compound additive.
2. the method for claim 1, it is characterized in that: described beta-silicon nitride powder principal crystalline phase is the α-Si that accounts for gross weight 85～95%
3N
4Powder.
3. method as claimed in claim 1 or 2 is characterized in that: the particle diameter of described beta-silicon nitride powder is 0.5～110 μ m.
4. the method for claim 1, it is characterized in that: described ammonium salt additive is selected from NH
4F, (NH
4)
2CO
3, NH
4The mixture of one or more among the Cl, when being selected from two or more mixed catalyst, the ratio between them such as is at a weight ratio.
5. the method for claim 1, it is characterized in that: described high energy mechanical activation treatment is meant that material grinds refinement and decrystallized in high-energy planetary formula ball mill, the horizontal rotor shredder of high energy, high energy vibrations shredder or stirring ball-milling machine equipment, and activation degree is no less than 5wt% with amorphous content;
Described mode of bringing out powder systems generation heat-producing chemical reaction comprises and adopts microwave heating, makes mode that heating element feeds 10～30 amperes electric current with tungsten helix or carbon paper and heat and realize.
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| CN100351170C (en) * | 2005-12-07 | 2007-11-28 | 北京科技大学 | Process for ordinary pressure continuous synthesizing silicon nitride powder by fluidized bed tech. |
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| CN102060544B (en) * | 2010-11-11 | 2015-06-17 | 北京科技大学 | Quick crystallization method for realizing amorphous silicon nitride powder by taking silica powder as additive |
| CN101983947A (en) * | 2010-11-24 | 2011-03-09 | 云南大学 | Novel method for synthesizing silicon nitride powder with high alpha phases by catalysis and nitridation |
| CN102219194A (en) * | 2011-05-16 | 2011-10-19 | 中国科学院唐山高新技术研究与转化中心 | Method for synthesizing silicon nitride or ferro silicon nitride by low-pressure preheating and burning |
| CN102503434B (en) * | 2011-09-30 | 2013-08-21 | 中国科学院理化技术研究所 | Method for synthesizing silicon nitride powder by nitriding silicon powder under condition of medium temperature and micro positive pressure |
| CN103318857B (en) * | 2013-07-10 | 2015-11-25 | 石家庄经济学院 | A kind of method of CVD synthesizing silicon nitride nano-rings |
| CN103553647B (en) * | 2013-10-08 | 2015-06-17 | 常州工程职业技术学院 | Method for preparation of silicon nitride bonded silicon carbide refractory material by using silicon cutting waste mortar |
| CN104876196A (en) * | 2015-05-08 | 2015-09-02 | 青岛桥海陶瓷新材料科技有限公司 | Preparation method for producing high purity beta-phase silicon nitride by combustion synthesis method |
| CN108609589B (en) * | 2018-04-13 | 2020-01-03 | 浙江东瓷新材料有限公司 | Silicon nitride powder suspension reactor |
| CN108996483B (en) * | 2018-10-26 | 2021-12-07 | 中国科学院理化技术研究所 | Method for synthesizing silicon nitride powder by combustion |
| CN109264677B (en) * | 2018-11-30 | 2020-05-12 | 西北农林科技大学 | Preparation method of silicon nitride rich in fiber morphology |
| CN109734456A (en) * | 2019-03-11 | 2019-05-10 | 中国科学院理化技术研究所 | A kind of preparation method of porous silicon nitride ceramic |
| CN109987943A (en) * | 2019-04-04 | 2019-07-09 | 天津大学 | A kind of preparation method of beta-silicon nitride powder |
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