CN103242044A - Gel-casting preparation method of BN/Si3N4 composite ceramics - Google Patents
Gel-casting preparation method of BN/Si3N4 composite ceramics Download PDFInfo
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- 239000000919 ceramic Substances 0.000 title claims abstract description 85
- 239000002131 composite material Substances 0.000 title claims abstract description 60
- 238000002360 preparation method Methods 0.000 title claims abstract description 33
- 238000005266 casting Methods 0.000 title claims abstract description 31
- 229910052581 Si3N4 Inorganic materials 0.000 title abstract description 7
- 239000000843 powder Substances 0.000 claims abstract description 101
- 239000002002 slurry Substances 0.000 claims abstract description 40
- 238000005245 sintering Methods 0.000 claims abstract description 31
- 238000001746 injection moulding Methods 0.000 claims abstract description 13
- 239000007787 solid Substances 0.000 claims abstract description 13
- 238000001035 drying Methods 0.000 claims abstract description 12
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- 238000002156 mixing Methods 0.000 claims abstract description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 31
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- 238000000034 method Methods 0.000 claims description 15
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- 239000000203 mixture Substances 0.000 claims description 12
- 239000000080 wetting agent Substances 0.000 claims description 12
- 239000008367 deionised water Substances 0.000 claims description 11
- 229910021641 deionized water Inorganic materials 0.000 claims description 11
- 238000001354 calcination Methods 0.000 claims description 8
- 150000003839 salts Chemical class 0.000 claims description 8
- 239000000725 suspension Substances 0.000 claims description 8
- 238000005303 weighing Methods 0.000 claims description 8
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- 238000000576 coating method Methods 0.000 claims description 7
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- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
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- 230000001681 protective effect Effects 0.000 claims description 4
- 238000004062 sedimentation Methods 0.000 claims description 4
- 238000007873 sieving Methods 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
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- 101100493705 Caenorhabditis elegans bath-36 gene Proteins 0.000 claims description 2
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- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 2
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Abstract
The invention relates to a gel-casting preparation method of BN/Si3N4 composite ceramics and aims at solving the problems that when the exiting BN/Si3N4 composite ceramics is subjected to gel casting, the solid content of slurry is low, and homogeneous dispersion of BN in a Si3N4 matrix is difficultly realized during gel casting. The preparation method comprises the steps of: 1, preparing a BN coated powder; 2, preparing a hybrid ceramic powder; 3, preparing the slurry; 4, adding an initiator and a catalyst into the slurry, mixing and carrying out injection molding to obtain a cured ceramic wet green body, and then drying the cured ceramic wet green body to obtain a dried green body; and 5, carrying out degreasing treatment on the dried green body in an air furnace, and then sintering the dried green body after degreasing treatment to obtain the BN/Si3N4 composite ceramics. The gel-casting preparation method is applied to the field of ceramic materials.
Description
Technical field
The present invention relates to a kind of gel casting forming preparation method of BN/Si3N4 complex phase ceramic.
Background technology
Silicon nitride (Si
3N
4) stupalith has high atom bonding strength, is one of best stupalith of over-all properties.It not only has excellent mechanical property and high thermostability (decomposition temperature is above 1900 ℃), and can regulate and control dielectric-constant adjustable (2～7) to density by the control of porosity.Its dielectric properties are very stable in room temperature to 1000 ℃ scope, and the thermal shock resistance excellence is very suitable for flight Mach number and is the manufacturing of 6～7 the saturating wave antenna cover of high-speed flight guided missile broadband.In addition, by at Si
3N
4Introduce the prepared BN/Si of part BN in the pottery
3N
4Composite ceramics can be in conjunction with Si
3N
4The high-mechanical property of pottery and the low-k of BN pottery and advantage such as can process, and composite ceramics can show fabulous chemical stability, high thermal shock resistance and have lower and stable specific inductivity and dielectric loss in the wide temperature range very much.Thereby, BN/Si
3N
4Composite ceramics has become at present one of the saturating wave climate selection of the most potential broadband material in the world.But, because Si
3N
4And the tooling cost of the low reliability of composite ceramics and costliness has limited the application process of its mass-producing.
The colloidal formation technology not only can be used for near-net-shape complicated shape ceramic green, reduce the ceramic component subsequent machining cost, and can also be used to reducing or eliminating defectives such as the reunion of the ceramic particle in the material, macroscopical pore, crackle, and then promote reliability of material.Gel casting forming is a forming technique that has potentiality in the colloidal formation technology, and it can prepare the uniform high-strength ceramic green compact of microstructure, can carry out mechanical preprocessing to framework in green article stage.
Preparation high solid loading, low viscous slurry are the prerequisites of gel injection molding and forming technology, still and have obtained the gel casting forming of the oxide ceramics of extensive application, Si
3N
4The gel casting forming suitability of pottery is relatively poor, particularly introduces BN and prepares BN/Si
3N
4During composite ceramics, the adding of BN makes the rapid variation of slurry fluidity.This mainly is because nitride powder easily produces some organo-functional groups in the surface, the cause of the alkalimetal ion of easy lingering section facile hydrolysis in the powder in process of production.Thereby have to realize BN/Si by the method that reduces the slurry solid load
3N
4The gel casting forming preparation technology of composite ceramics, but during slurry solid load step-down, cause wet base shrinking percentage in drying process to increase, be easy to generate warpage, be unfavorable for realizing the near-net-shape of member.
In addition, at preparation BN/Si
3N
4During composite ceramics, because BN is at Si
3N
4In difficult dispersion, prepared material is difficult to realize uniform heterogeneous microstructure, and the existence of BN also can hinder the mass transfer in liquid phase process in the liquid phase sintering process, is unfavorable for densification and the α-Si of material
3N
4To β-Si
3N
4Phase transition, thereby can cause very macrolesion to the mechanical property of material.
Summary of the invention
The present invention will solve present BN/Si
3N
4Low and the BN of slurry solid load is at Si during the gel casting forming of complex phase ceramic
3N
4The homodisperse problem of difficult realization provides a kind of BN/Si in the matrix
3N
4The gel casting forming preparation method of complex phase ceramic.
A kind of BN/Si of the present invention
3N
4The gel casting forming preparation method of complex phase ceramic, realize according to the following steps:
One, adopts the inorganic salt sedimentation to prepare Y/Al salt coating at the BN powder surface, after calcining, sieving, obtain the BN coated composite powder;
Two, by volume umber takes by weighing Si
3N
4, BN coated composite powder and sintering aid, obtain the hybrid ceramic powder; Si wherein
3N
4Volume parts greater than 60 parts less than 100 parts, the volume parts of BN coated composite powder greater than 0 part less than 40 parts, the volume parts of sintering aid greater than 5 parts less than 10 parts;
Three, in deionized water, add organic monomer, linking agent, wetting agent and dispersion agent, obtain premixed liquid, be that 28% ammoniacal liquor and quality percentage composition are pH value to 9～11 that 10% hydrochloric acid is regulated premixed liquid with the quality percentage composition then, add the hybrid ceramic powder again, ball milling mixes then, obtains slurry; Wherein the solid load of ceramic powder is 35～45vol.% in the slurry; The add-on of organic monomer is 3～8wt.% of ceramic powder total mass, the add-on of dispersion agent is 0.2～0.6wt.% of ceramic powder total mass, the add-on of wetting agent is 2～6wt.% of ceramic powder total mass, and the mass ratio of organic monomer and linking agent is (5～15): 1;
Four, add initiator and catalyzer in the slurry that step 3 obtains, carry out injection molding after the stirring, the pottery that obtains the solidifying base that wets carries out drying then, obtains dried green compact;
Five, dried green compact are carried out skimming treatment in air furnace, carry out sintering then, obtain BN/Si
3N
4Complex phase ceramic is namely finished BN/Si
3N
4The gel casting forming preparation of complex phase ceramic.
The present invention introduces BN by the form with the BN coated powder, can realize that solid load is 44vol.%, and the BN/Si of the very suitable gel injection molding and forming technology of viscosity
3N
4The preparation of composite mortar has solved gel injection molding and forming technology and has prepared BN/Si
3N
4The introducing of BN causes the problem of the rapid variation of slurry viscosity during composite ceramics; And introduce with the form of coated powder by BN, realized the even dispersion of BN in slurry, solved BN at Si
3N
4The homodisperse problem of difficult realization is finally prepared the uniform BN/Si of heterogeneous microstructure in the matrix
3N
4Composite ceramics, and material has excellent mechanical property and lower specific inductivity, can be used as the carrying under the severe condition, saturating ripple, thermally protective materials, is used for fields such as aerospace, mechanical industry.
Description of drawings
Fig. 1 is that the shear viscosity of slurry in test 1 control group is with the variation relation of shearing rate;
Be the add-on of the original powder of BN prepared slurry when by volume umber is 5 parts;
Be the add-on of the original powder of BN prepared slurry when by volume umber is 10 parts;
Be the add-on of the original powder of BN prepared slurry when by volume umber is 15 parts;
Be the add-on of the original powder of BN prepared slurry when by volume umber is 20 parts;
Fig. 2 is the projection light field phase photo of BN coated composite powder in test 1 test group;
Fig. 3 is that the shear viscosity of slurry in test 12 test group is with the variation relation of shearing rate;
Be the add-on of BN coated composite powder prepared slurry when by volume umber is 5 parts;
Be the add-on of BN coated composite powder prepared slurry when by volume umber is 10 parts;
Be the add-on of BN coated composite powder prepared slurry when by volume umber is 15 parts;
Be the add-on of BN coated composite powder prepared slurry when by volume umber is 20 parts.
Embodiment
Embodiment one: a kind of BN/Si of present embodiment
3N
4The gel casting forming preparation method of complex phase ceramic, realize according to the following steps:
One, adopts the inorganic salt sedimentation to prepare Y/Al salt coating at the BN powder surface, after calcining, sieving, obtain the BN coated composite powder;
Two, by volume umber takes by weighing Si
3N
4, BN coated composite powder and sintering aid, obtain the hybrid ceramic powder; Si wherein
3N
4Volume parts greater than 60 parts less than 100 parts, the volume parts of BN coated composite powder greater than 0 part less than 40 parts, the volume parts of sintering aid greater than 5 parts less than 10 parts;
Three, in deionized water, add organic monomer, linking agent, wetting agent and dispersion agent, obtain premixed liquid, be that 28% ammoniacal liquor and quality percentage composition are pH value to 9～11 that 10% hydrochloric acid is regulated premixed liquid with the quality percentage composition then, add the hybrid ceramic powder again, ball milling mixes then, obtains slurry; Wherein the solid load of ceramic powder is 35～45vol.% in the slurry; The add-on of organic monomer is 3～8wt.% of ceramic powder total mass, the add-on of dispersion agent is 0.2～0.6wt.% of ceramic powder total mass, the add-on of wetting agent is 2～6wt.% of ceramic powder total mass, and the mass ratio of organic monomer and linking agent is (5～15): 1;
Four, add initiator and catalyzer in the slurry that step 3 obtains, carry out injection molding after the stirring, the pottery that obtains the solidifying base that wets carries out drying then, obtains dried green compact;
Five, dried green compact are carried out skimming treatment in air furnace, carry out sintering then, obtain BN/Si
3N
4Complex phase ceramic is namely finished BN/Si
3N
4The gel casting forming preparation of complex phase ceramic.
Present embodiment is introduced BN by the form with the BN coated powder, can realize that solid load is 44vol.%, and the BN/Si of the very suitable gel injection molding and forming technology of viscosity
3N
4The preparation of composite mortar has solved gel injection molding and forming technology and has prepared BN/Si
3N
4The introducing of BN causes the problem of the rapid variation of slurry viscosity during composite ceramics; And introduce with the form of coated powder by BN, realized the even dispersion of BN in slurry, solved BN at Si
3N
4The homodisperse problem of difficult realization is finally prepared the uniform BN/Si of heterogeneous microstructure in the matrix
3N
4Composite ceramics, and material has excellent mechanical property and lower specific inductivity, can be used as the carrying under the severe condition, saturating ripple, thermally protective materials, is used for fields such as aerospace, mechanical industry.
Embodiment two: what present embodiment and embodiment one were different is that the BN coated composite powder is realized according to the following steps in the step 1: one, take by weighing 200mL deionized water, 15g Al (NO
3)
3, 21.16g Y (NO
3)
3With 10g urea, add in the deionized water, solution is heated to 95 ℃ then, insulation 1～2h is cooled to room temperature subsequently, obtains premixed liquid; Two, take by weighing 51.9g BN, join in the 800mL deionized water, through ball mill mixing 5～24h, obtain BN suspension; Three, premixed liquid is added BN suspension, at 50～60 ℃ of stirred in water bath 36～48h, obtain the mixture of premixed liquid and BN suspension; Four, the premixed liquid that obtains and the mixture of BN suspension are dried in 60～120 ℃ baking oven, grind the back and cross 100～120 mesh sieves, obtain the BN powder that Y/Al salt coats; Five, the BN powder that Y/Al salt is coated is put into tube furnace in the N of 0.05～0.1MPa
2Under the protective atmosphere, 800～1200 ℃ of calcining 1～2h obtain the BN coated composite powder.Other steps are identical with embodiment one with parameter.
Embodiment three: what present embodiment was different with embodiment one or two is that sintering aid is Al in the step 2
2O
3And Y
2O
3Be 1 by volume: the mixed of (1.5～3) forms.Other steps are identical with embodiment one or two with parameter.
Embodiment four: present embodiment is different with one of embodiment one to three is that time of ball milling in the step 3 is 10～24h, and ball material mass ratio is (1～1.5): 1.Other steps are identical with one of embodiment one to three with parameter.
Embodiment five: what present embodiment was different with one of embodiment one to four is that organic monomer is acrylamide in the step 3; Linking agent is N, N '-methylene-bisacrylamide; Wetting agent is poly(oxyethylene glycol) 400; Dispersion agent is polyacrylic acid.Other steps are identical with one of embodiment one to four with parameter.
Embodiment six: present embodiment is different with one of embodiment one to five is that initiator in the step 4 is ammonium persulphate, and add-on is 3～8wt.% of ceramic powder total mass.Other steps are identical with one of embodiment one to five with parameter.
Embodiment seven: present embodiment is different with one of embodiment one to six is that catalyzer in the step 4 is N, N, N ' N '-Tetramethyl Ethylene Diamine, the volume ratio of catalyzer and premixed liquid (2～6) mL: L.Other steps are identical with one of embodiment one to six with parameter.
Embodiment eight: present embodiment is different with one of embodiment one to seven is that drying process in the step 4 is carried out in climatic chamber, and dry initial humidity control is 50～100%, and temperature is controlled at 20～30 ℃; After contraction to be dried stops, humidity is reduced to 30～50%, temperature is increased to 30～60 ℃, finishes until drying process.Other steps are identical with one of embodiment one to seven with parameter.
Embodiment nine: present embodiment is different with one of embodiment one to eight is that skimming processes in the step 5 is to carry out in air furnace, and skimming temp is 500～800 ℃, insulation 1～2h, and temperature rise rate is controlled at 0.5～2 ℃/min.Other steps are identical with one of embodiment one to eight with parameter.
Embodiment ten: present embodiment is different with one of embodiment one to nine is that sintering in the step 5 is to carry out in atmosphere sintering furnace, with the N of 0.1～0.6MPa
2Be shielding gas, temperature rise rate is 10～30 ℃/min, and sintering temperature is 1700～1800 ℃, soaking time 1～3h.Other steps are identical with one of embodiment one to nine with parameter.
By following verification experimental verification beneficial effect of the present invention:
Test 1, this test are divided into test group and control group.
The BN/Si of control group
3N
4The gel casting forming preparation method of complex phase ceramic, BN introduces with the form of original powder, carries out according to the following steps:
One, by volume umber takes by weighing 75～90 parts of Si
3N
4, 5～20 parts of BN, 3.5 parts of Y
2O
3Powder and 1.5 parts of Al
2O
3Powder obtains the hybrid ceramic powder;
Two, adding organic monomer, linking agent, wetting agent and dispersion agent in deionized water, obtain premixed liquid, is the pH value to 10 that 28% ammoniacal liquor is regulated premixed liquid with the quality percentage composition then, adds mixed powder again, and ball milling mixing then obtains slurry; Wherein the solid load of ceramic powder is 40vol.% in the slurry; The add-on of organic monomer is the 5wt.% of ceramic powder total mass, and the add-on of dispersion agent is the 0.4wt.% of ceramic powder total mass, and the add-on of wetting agent is the 3wt.% of ceramic powder total mass, and the mass ratio of organic monomer and linking agent is 15: 1;
Three, add initiator and catalyzer in the slurry that step 2 obtains, carry out injection molding after the stirring, the pottery that obtains the solidifying base that wets carries out drying then, obtains dried green compact;
Four, dried green compact are carried out skimming treatment in air furnace, carry out sintering then, obtain BN/Si
3N
4Complex phase ceramic.
Drying process in this testing sequence three at first be 90% in humidity, temperature is dry 2～3d in 35 ℃ the climatic chamber, afterwards humidity is adjusted into 30%, 50 ℃ of down dry 2～3d of temperature; Skimming processes is to carry out in air furnace in the step 4, and calcining temperature is 600 ℃, insulation 1h, and temperature rise rate is controlled at 2 ℃/min; Sintering process is to carry out in atmosphere sintering furnace, with the N of 0.1MPa
2Be shielding gas, temperature rise rate is controlled at 20 ℃/min, and sintering temperature is 1750 ℃, soaking time 1h.
In this test, when adopting rotational viscosimeter by volume umber being respectively 5,10,15 and 20 parts to the add-on of the original powder of BN, prepared BN/Si
3N
4The viscosity of composite mortar is measured, and slurry viscosity with the variation relation curve of shearing rate as shown in Figure 1.As can be seen from the figure, along with the increase of BN introducing amount in the raw material, the viscosity of composite mortar all increases in shearing rate is the scope of 5～95r/min gradually.But, overall on the viscosity number of four groups of samples all in 1000mPas, all be relatively to be suitable for gel injection molding and forming technology.
The add-on of the original powder of BN Si when by volume umber is 5 parts in this test
3N
4Add-on by volume umber be 90 parts, the add-on of the original powder of BN Si when by volume umber is 10 parts
3N
4Add-on by volume umber be 85 parts, the add-on of the original powder of BN Si when by volume umber is 15 parts
3N
4Add-on by volume umber be 80 parts, the add-on of the original powder of BN Si when by volume umber is 20 parts
3N
4Add-on by volume umber be 75 parts.
The add-on of the original powder of BN is respectively 5,10,15 and 20 parts in this test, prepared BN/Si
3N
4Composite ceramics is called after 5BS, 10BS, 15BS and 20BS respectively, and density, bending strength and the specific inductivity of material characterized, and test result is as shown in table 1.As can be seen from the table, along with the increase of the original powder introducing of BN in raw material amount, BN/Si
3N
4The density of composite ceramics descends gradually, correspondingly, bending strength and specific inductivity also descend gradually, this explanation is along with the increase of BN introducing amount, the effect that hinders the material sintering densification is also more and more obvious, and in expendable material part mechanical property, can bring the reduction significantly of specific inductivity.
Table 1
The BN/Si of test group
3N
4The gel casting forming preparation method of complex phase ceramic, realize according to the following steps:
One, adopts the inorganic salt sedimentation to prepare one deck Y/Al salt coating at the BN powder surface, after calcining, sieving, obtain the BN coated composite powder;
Two, with Si
3N
4, BN coated composite powder, Y
2O
3Powder and Al
2O
3Powder mixes, and obtains the hybrid ceramic powder; Wherein contain Y in the BN coated composite powder
2O
3And Al
2O
3, then with Y
2O
3Volume parts complement to 3.5 parts and Al
2O
3Volume parts complement to 1.5 parts.
Three, adding organic monomer, linking agent, wetting agent and dispersion agent in deionized water, obtain premixed liquid, is the pH value to 10 that 28% ammoniacal liquor is regulated premixed liquid with the quality percentage composition then, adds mixed powder again, and ball milling mixing then obtains slurry; Wherein the solid load of ceramic powder is 40vol.% in the slurry; The add-on of organic monomer is the 5wt.% of ceramic powder total mass, and the add-on of dispersion agent is the 0.4wt.% of ceramic powder total mass, and the add-on of wetting agent is the 3wt.% of ceramic powder total mass, and the mass ratio of organic monomer and linking agent is 15: 1;
Four, add initiator and catalyzer in the slurry that step 2 obtains, carry out injection molding after the stirring, the pottery that obtains the solidifying base that wets carries out drying then, obtains dried green compact;
Five, dried green compact are carried out skimming treatment in air furnace, carry out sintering then, obtain BN/Si
3N
4Complex phase ceramic.
The method of this test BN coated composite powder adopts the method for embodiment two to carry out, drying process in this testing sequence four at first be 90% in humidity, temperature is to be dried to 2～3d in 35 ℃ the climatic chamber, afterwards humidity is adjusted into 30%, 50 ℃ of down dry 2～3d of temperature; Skimming processes is to carry out in air furnace in the step 5, and calcining temperature is 600 ℃, insulation 1h, and temperature rise rate is controlled at 2 ℃/min; Sintering process is to carry out in atmosphere sintering furnace, with the N of 0.1MPa
2Be shielding gas, temperature rise rate is controlled at 20 ℃/min, and sintering temperature is 1750 ℃, soaking time 1h.
In this test, the projection light field phase photo of powder as shown in Figure 2 after BN coated, the zone that shown coating BN grain edges contrast is different among the figure has formed one deck at the BN particle surface and has been about tens nanometers to the coating layer zone of up to a hundred nano thickness as can be seen after coating.Though the thickness of this coating layer is very uneven, and the combination of BN particle still comparatively closely, and this photo shows that also coating layer realizes the BN particle is coated fully substantially.
When adopting rotational viscosimeter by volume umber being respectively 5,10,15 and 20 parts to the add-on of BN coated composite powder, prepared BN/Si
3N
4The viscosity of composite mortar is measured, and slurry viscosity with the variation relation curve of shearing rate as shown in Figure 3.As can be seen from the figure, along with the increase of BN coated composite powder introducing amount in the raw material, the viscosity of composite mortar all increases in shearing rate is the scope of 5～95r/min gradually.But, overall on the viscosity number of four groups of samples all in 1000mPas, all be relatively to be suitable for gel injection molding and forming technology.Compare and can find with Fig. 1, BN can significantly reduce the viscosity of slurry when introducing with the form of coated powder.
The add-on of BN coated composite powder Si when by volume umber is 5 parts in this test
3N
4Add-on by volume umber be 90 parts, the add-on of BN coated composite powder Si when by volume umber is 10 parts
3N
4Add-on by volume umber be 85 parts, the add-on of BN coated composite powder Si when by volume umber is 15 parts
3N
4Add-on by volume umber be 80 parts, the add-on of BN coated composite powder Si when by volume umber is 20 parts
3N
4Add-on by volume umber be 75 parts.The volume parts that adds the BN coated composite powder in this test is to calculate by the volume parts of BN in the BN coated composite powder.
In this test the add-on of BN coated composite powder by volume umber be respectively 5,10,15 and 20 parts, prepared BN/Si
3N
4Composite ceramics is called after 5CBS, 10CBS, 15CBS and 20CBS respectively, and density, bending strength and the specific inductivity of material characterized, and test result is as shown in table 1.As can be seen from the table, along with the increase of raw material coating BN powder introducing amount, BN/Si
3N
4The density of composite ceramics descends gradually, correspondingly, bending strength and specific inductivity also descend gradually, this explanation is along with the increase of BN coated composite powder introducing amount, the effect that hinders the material sintering densification is also more and more obvious, and in expendable material part mechanical property, can bring the reduction significantly of specific inductivity.But by comparing and can find with table 1, except BN content is the sample of 5vol.%, for other three groups of samples, when BN introduces with the form of coated powder, prepared BN/Si
3N
4The sintering characteristic of composite ceramics be improved significantly, be in particular in that the density of sample 10CBS, 15CBS and 20CBS and bending strength all will be higher than sample 10BS, 15BS and 20BS.
Table 2
Test 1 by among the embodiment and test 2 be as can be known: by contain the coating layer of Y/Al oxide compound at BN ceramic powder surface preparation one deck, can make BN/Si
3N
4The rheologic behavio(u)r of composite mortar is greatly improved, the BN/Si of more favourable preparation high solid loading
3N
4Composite mortar; And when BN introduced with the form of coated powder, when introducing with former powder form with respect to the BN of same amount, sintered density and the bending strength of material all improved a lot, and the sintering characteristic of illustrative material can be greatly improved.
Claims (10)
1. BN/Si
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that BN/Si
3N
4The gel casting forming preparation method of complex phase ceramic realizes according to the following steps:
One, adopts the inorganic salt sedimentation to prepare Y/Al salt coating at the BN powder surface, after calcining, sieving, obtain the BN coated composite powder;
Two, by volume umber takes by weighing Si
3N
4, BN coated composite powder and sintering aid, obtain ceramic powder; Si wherein
3N
4Volume parts greater than 60 parts less than 100 parts, the volume parts of BN coated composite powder greater than 0 part less than 40 parts, the volume parts of sintering aid greater than 5 parts less than 10 parts;
Three, in deionized water, add organic monomer, linking agent, wetting agent and dispersion agent, obtaining premixed liquid, is that 28% ammoniacal liquor and quality percentage composition are pH value to 9～11 that 10% hydrochloric acid is regulated premixed liquid with the quality percentage composition then, adds ceramic powder again, ball milling mixes then, obtains slurry; Wherein the solid load of ceramic powder is 35～45vol.% in the slurry; The add-on of organic monomer is 3～8wt.% of ceramic powder total mass, the add-on of dispersion agent is 0.2～0.6wt.% of ceramic powder total mass, the add-on of wetting agent is 2～6wt.% of ceramic powder total mass, and the mass ratio of organic monomer and linking agent is (5～15): 1;
Four, add initiator and catalyzer in the slurry that step 3 obtains, carry out injection molding after the stirring, the pottery that obtains the solidifying base that wets carries out drying then, obtains dried green compact;
Five, dried green compact are carried out skimming treatment in air furnace, carry out sintering then, obtain BN/Si
3N
4Complex phase ceramic is namely finished BN/Si
3N
4The gel casting forming preparation of complex phase ceramic.
2. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that the preparation method of the BN coated composite powder described in the step 1 realizes according to the following steps: one, take by weighing 200ml deionized water, 15g Al (NO
3)
3, 21.16g Y (NO
3)
3With 10g urea, add in the deionized water, liquid is heated to 95 ℃ then, and insulation 1～2h is cooled to room temperature subsequently, obtains premixed liquid; Two, take by weighing 51.9g BN, join in the 800mL deionized water, through ball mill mixing 5～24h, obtain BN suspension; Three, premixed liquid is added BN suspension, at 50～60 ℃ of stirred in water bath 36～48h, obtain the mixture of premixed liquid and BN suspension; Four, the premixed liquid that obtains and the mixture of BN suspension are dried in 60～120 ℃ baking oven, grind the back and cross 100～120 mesh sieves, obtain the BN powder that Y/Al salt coats; Five, the BN powder that Y/Al salt is coated is put into tube furnace in the N of 0.05～0.1MPa
2Under the protective atmosphere, 800～1200 ℃ of calcining 1～2h obtain the BN coated composite powder.
3. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that sintering aid is Al in the step 2
2O
3And Y
2O
3Be 1 by volume: the mixed of (1.5～3) forms.
4. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic, the time that it is characterized in that ball milling in the step 3 is 10～24h, ball material mass ratio is (1～1.5): 1.
5. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that organic monomer is acrylamide in the step 3; Linking agent is N, N '-methylene-bisacrylamide; Wetting agent is poly(oxyethylene glycol) 400; Dispersion agent is polyacrylic acid.
6. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that the initiator in the step 4 is ammonium persulphate, and add-on is 3～8wt.% of ceramic powder total mass.
7. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that the catalyzer in the step 4 is N, N, N ' N '-Tetramethyl Ethylene Diamine, the volume ratio of catalyzer and premixed liquid (2～6) mL: L.
8. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that the drying process in the step 4 is carried out in climatic chamber, dry initial humidity control is 50～100%, and temperature is controlled at 20～30 ℃; After contraction to be dried stops, humidity is reduced to 30～50%, temperature is increased to 30～60 ℃, keeps 2～3d, obtains dried green compact.
9. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that the skimming processes in the step 5 is to carry out in air furnace, skimming temp is 500～800 ℃, insulation 1～2h, and temperature rise rate is 0.5～2 ℃/min.
10. a kind of BN/Si according to claim 1
3N
4The gel casting forming preparation method of complex phase ceramic is characterized in that the sintering in the step 5 is to carry out, with the N of 0.1～0.6MPa in atmosphere sintering furnace
2Be shielding gas, temperature rise rate is 10～30 ℃/min, and sintering temperature is 1700～1800 ℃, soaking time 1～3h.
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